KAT ll INHIBITORS

ABSTRACT

Compounds of Formula I: 
     
       
         
         
             
             
         
       
     
     wherein X, Y, Z, R 1 , R 2 , R 3 , R 4  are as defined herein, and pharmaceutically acceptable salts thereof, are described as useful for the treatment of cognitive deficits associated with schizophrenia and other psychiatric, neurodegenerative and/or neurological disorders in mammals, including humans.

This application claims the benefit of priority to U.S. provisionalpatent application Ser. No. 61/418,802 filed Dec. 1, 2010, thedisclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the treatment of cognitive deficitsassociated with schizophrenia and other psychiatric, neurodegenerativeand/or neurological disorders in mammals, including humans. Moreparticularly, this invention relates to bicyclic inhibitors of the KATII enzyme, useful for the treatment of such disorders.

BACKGROUND OF THE INVENTION

KAT (kynurenine aminotransferase) II is a primary enzyme in the brainfor catalyzing the transamination of kynurenine to KYNA (kynurenic acid)(E. Okuno et al., J. Neurochem., vol. 57, 533-540, 1991). KYNA is aneffective excitatory amino acid (EAA) receptor antagonist with affinityfor the glycine modulatory site of the N-methyl-D-aspartate (NMDA)receptor complex (M. Kessler et al., J. Neurochem., vol. 52, pp.1319-1328, 1989). As a naturally occurring brain metabolite, KYNAprobably serves as a negative endogenous modulator of cerebralglutamatergic function (R. Schwarcz et al., Ann. N.Y. Acad. Sci., vol.648, pp. 140-153, 1992), and activator of arylhydrocarbon receptors (B.DiNatale et al., Toxicol. Sci. vol 115, pp. 89-97, 2010).

EAA receptors and in particular NMDA receptors are known to play acentral role in the function of the mammalian brain (J. C. Watkins andG. L. Collingridge, Eds., The NMDA Receptor, Oxford University Press,Oxford, 1989, p. 242). For example, NMDA receptor activation isessential for cognitive processes, such as, for example, learning andmemory (Watkins and Collingridge, supra, pp. 137-151). Therefore,reducing KYNA synthesis by inhibition of its synthetic enzyme mayenhance EAA signaling and improve cognitive processes, especially indisease states where NMDA hypofunction is anticipated. Thus, there is aneed for compounds which act as KAT II inhibitors to reduce KYNAsynthesis within the brain to improve cognitive dysfunction in humandisease states.

SUMMARY OF THE INVENTION

The present invention is directed to compounds of Formula I:

or a pharmaceutically acceptable salt thereof, wherein

solid circle represents single or double bonds as valency requires;

X, Y, and Z are independently selected from a group consisting of ═N—,—N═, NR¹, and CR², provided that at least two are other than CR²;

R¹ is H, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl,SO₂NR⁵R⁶, or SO₂R^(5a), wherein each said alkyl, cycloalkyl,heterocycloalkyl, aryl, aralkyl, and heteroaryl may be substituted withone or more substituents independently selected from hydroxy, amino,halo, alkyl, haloalkyl, CN, alkoxy, haloalkoxy, alkylamino, aminoalkyl,—(CH₂)_(n)cycloalkyl, —(CH₂)_(n)heterocycloalkyl, —(CH₂)_(n)aryl, and—(CH₂)_(n)heteroaryl;

R² is H, halo, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl,heteroaryl, alkoxy, cycloalkyloxy, aryloxy, aralkyloxy,heterocycloalkyloxy, heteroaryloxy, CN, —(CH₂)_(n)NR⁵R⁶, C(═O)NR⁵R⁶,SO₂NR⁵R⁶, SO₂R^(5a), NR⁵SO₂R^(5a), or NR⁵C(═O)R^(5a), wherein each saidalkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkoxy,cycloalkyloxy, aryloxy, aralkyloxy, heterocycloalkyloxy, andheteroaryloxy may be substituted with one or more substituentsindependently selected from hydroxy, amino, halo, alkyl, haloalkyl, CN,alkoxy, haloalkoxy, alkylamino, aminoalkyl, —(CH₂)_(n)cycloalkyl,—(CH₂)_(n)heterocycloalkyl, —(CH₂)_(n)aryl, and —(CH₂)_(n)heteroaryl;

R³ is H, C(═O)R⁷, C(═O)OR⁷, C(═O)NR^(7a)R^(7b), or (CH₂)R⁸;

each R⁴ is independently H, methyl, or fluoromethyl;

R⁵ and R⁶ are independently H, alkyl, fluoroalkyl, aryl, or heteroaryl,or

R⁵ and R⁶ of C(═O)NR⁵R⁶ or SO₂NR⁵R⁶, together with the nitrogen to whichthey are attached, may form a heterocycloalkyl;

R^(5a) is alkyl, fluoroalkyl, aryl, or heteroaryl;

R⁷ is alkyl, aryl, heteroaryl, or cycloalkyl, wherein each said alkyl,aryl, heteroaryl, and cycloalkyl may be substituted with one or moresubstituents independently selected from hydroxy, amino, halo, alkoxy,and aminoalkyl;

R^(7a) and R^(7b) are independently H, alkyl, aryl, heteroaryl, orcycloalkyl, wherein each said alkyl, aryl, heteroaryl, and cycloalkylmay be substituted with one or more substituents independently selectedfrom hydroxy, amino, halo, alkoxy, and aminoalkyl, or, when R³ isC(═O)NR^(7a)R^(7b), R^(7a) and R^(7b), together with the nitrogen atomto which they are attached, may form a 5- or 6-membered N-containingheterocyclic ring;

R⁸ is

R⁹ is H, alkyl, aryl, heteroaryl, or cycloalkyl, wherein each saidalkyl, aryl, heteroaryl, and cycloalkyl may be substituted with one ormore substituents independently selected from hydroxy, amino, halo,alkoxy, and aminoalkyl; and

each n is independently 0, 1, 2, or 3.

This invention also includes pharmaceutically acceptable salts,hydrates, solvates, isomers, crystalline and non-crystalline forms,isomorphs, polymorphs, and metabolites of compounds of Formula I. Thisinvention also includes all tautomers and stereochemical isomers ofthese compounds.

This invention also is directed, in part, to a method for treating a KATII-mediated disorder in a mammal. Such disorders include cognitivedeficits associated with schizophrenia and other psychiatric,neurodegenerative and/or neurological disorders. The method comprisesadministering a compound of Formula I or a pharmaceutically acceptablesalt thereof, to the mammal in an amount that is therapeuticallyeffective to treat the condition.

When introducing elements of the present invention or the exemplaryembodiment(s) thereof, the articles “a,” “an,” “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising,” “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. Although this invention has been described with respect tospecific embodiments, the details of these embodiments are not to beconstrued as limitations to the invention, the scope of which is definedby the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention is a compound of Formula I asdescribed above.

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein one of X or Y isNR¹ and the other is —N═ or ═N—; Z is CR²; R¹ is C₁ to C₆ alkyl; C₃ toC₆ cycloalkyl, aryl, or arylalkyl; R² is H, C₁ to C₆ alkyl, C₃ to C₆cycloalkyl, aryl or arylalkyl; and wherein each said alkyl, cycloalkyl,aryl, and arylalkyl may be substituted as allowed in Formula I and R³and R⁴ are as defined in any embodiment of Formula I.

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein X is NR¹; Y is—N═ or ═N—; Z is CR²; and wherein R¹, R², R³, and R⁴ are as defined inany embodiment of Formula I. In one such embodiment, the compound ofFormula I has the following structure:

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein the alkyl of R¹is C₁ to C₃ alkyl; and R², R³, and R⁴ are as defined in any embodimentof Formula I.

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein the aryl of R¹and R² is phenyl or naphthyl, and the arylalkyl of R¹ and R² is—CH₂-phenyl or —CH₂-naphthyl, and wherein any phenyl or naphthyl may besubstituted with one or more substituents independently selected fromhalo, alkyl (e.g., C₁ to C₃ alkyl), haloalkyl (e.g., CF₃), alkoxy (e.g.,methoxy), haloalkoxy (e.g., CF₃—O), and CN.

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein X is —N═ or ═N—;Y is NR¹; Z is CR²; R¹ is C₁ to C₆ alkyl; R² is H, aryl or arylalkyl;and wherein each said alkyl, aryl, and arylalkyl may be substituted asdefined in Formula I, and wherein R³ and R⁴ are as defined in anyembodiment of Formula I. In one such embodiment, the compound of FormulaI has the following structure:

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein the aryl of R² isphenyl or naphthyl, and the arylalkyl of R² is —CH₂-phenyl or—CH₂-naphthyl, and wherein any phenyl or naphthyl may be substitutedwith one or more substituents independently selected from halo, alkyl(e.g., C₁ to C₃ alkyl), haloalkyl (e.g., CF₃), alkoxy (e.g., methoxy),haloalkoxy (e.g., CF₃—O), and CN, and wherein R¹, R³ and R⁴ are asdefined in any embodiment of Formula I.

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein X is CR²; Y isNR¹; and Z is —N═ or ═N—; R¹ is H, C₁ to C₆ alkyl, aryl or arylalkyl; R²is H or C₁ to C₃ alkyl; and wherein each said alkyl, aryl, and arylalkylmay be substituted as allowed in any embodiment of Formula I and R³ andR⁴ are as defined in any embodiment of Formula I. In one suchembodiment, the compound of Formula I has the followinh structure:

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein X is CR²; Y is—N═ or ═N—; and Z is NR¹; R¹ is H, C₁ to C₆ alkyl, aryl or arylalkyl; R²is H or C₁ to C₃ alkyl; and wherein each said alkyl, aryl, and arylalkylmay be substituted as allowed in any embodiment of Formula I and R³ andR⁴ are as defined in any embodiment of Formula I. In one suchembodiment, the compound of Formula I has the following structure:

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein aryl of R¹ isphenyl or naphthyl, and the arylalkyl of R¹ is —CH₂-phenyl or—CH₂-naphthyl, and wherein any phenyl or naphthyl may be substitutedwith one or more substituents selected from halo, alkyl (e.g., C₁ to C₃alkyl), haloalkyl (e.g., CF₃), alkoxy (e.g., methoxy), haloalkoxy (e.g.,CF₃—O), and CN and R², R³ and R⁴ are as defined in any embodiment ofFormula I.

Furthermore, by way of example and not as a limitation, when aryl andarylalkyl are specified for R¹ and R², R¹ and R² may be any othervariable as allowed in Formula I. When such definitions are used R¹ andR² may have the following definitions:

R¹ is H, alkyl, cycloalkyl, heterocycloalkyl, phenyl, naphthyl,—CH₂-phenyl, —CH₂-naphthyl, heteroaryl, SO₂NR⁵R⁶, or SO₂R^(5a), whereineach said alkyl, cycloalkyl, heterocycloalkyl, phenyl, naphthyl,—CH₂-phenyl, —CH₂-naphthyl, and heteroaryl may be substituted with oneor more substituents independently selected from hydroxy, amino, halo,alkyl, haloalkyl, CN, alkoxy, haloalkoxy, alkylamino, aminoalkyl,—(CH₂)_(n)cycloalkyl, —(CH₂)_(n)heterocycloalkyl, —(CH₂)_(n)aryl, and—(CH₂)_(n)heteroaryl;

R² is H, halo, alkyl, cycloalkyl, heterocycloalkyl, phenyl, naphthyl,—CH₂-phenyl, —CH₂-naphthyl, heteroaryl, alkoxy, cycloalkyloxy, aryloxy,aralkyloxy, heterocycloalkyloxy, heteroaryloxy, CN, —(CH₂)_(n)NR⁵R⁶,C(═O)NR⁵R⁶, SO₂NR⁵R⁶, SO₂R^(5a), NR⁵SO₂R^(5a), or NR⁵C(═O)R^(5a),wherein each said alkyl, cycloalkyl, heterocycloalkyl, phenyl, naphthyl,—CH₂-phenyl, —CH₂-naphthyl, heteroaryl, alkoxy, cycloalkyloxy, aryloxy,aralkyloxy, heterocycloalkyloxy, and heteroaryloxy may be substitutedwith one or more substituents independently selected from hydroxy,amino, halo, alkyl, haloalkyl, CN, alkoxy, haloalkoxy, alkylamino,aminoalkyl, —(CH₂)_(n)cycloalkyl, —(CH₂)_(n)heterocycloalkyl,—(CH₂)_(n)aryl, and —(CH₂)_(n)heteroaryl.

Therefore, what is intended is that “phenyl, naphthyl,” replace aryl and“—CH₂-phenyl, —CH₂-naphthyl,” replace arylalkyl within any definition ofR¹ and R² presented in the embodiments herein without having to repeatall definitions of R¹ or R². Hence, it includes where R¹ or R² may bedefined in any embodiment. For example, R¹ may be defined as H, C₁ to C₆alkyl, aryl or arylalkyl such that it would mean R¹ is H, C₁ to C₆alkyl, phenyl, naphthyl, —CH₂-phenyl or —CH₂-naphthyl. It also includeswhere R² may be defined as H, aryl or arylalkyl such that it would meanR² would be H, phenyl, naphthyl, —CH₂-phenyl or —CH₂-naphthyl.Furthermore, R¹ may be defined as C₁ to C₆ alkyl; C₃ to C₆ cycloalkyl,aryl, or arylalkyl and R² may be defined as H, C₁ to C₆ alkyl, C₃ to C₆cycloalkyl, aryl or arylalkyl such that each aryl and arylalkyl withinsaid definition is replaced “phenyl, naphthyl,” and “—CH₂-phenyl,—CH₂-naphthyl”, respectively.

Moreover, the explanation of aryl/arylalkyl within the definitionsapplies to other variables within the R groups of Formula I. Forexample, when referencing alkyl, all other definitions possible areincluded but not repeated when alkyl may be limited to, e.g., C₁ to C₃alkyl. For brevity, the complete list of variables for the definition ofthe specific R group is not repeated.

Another embodiment of the present invention is a compound of Formula I,or a pharmaceutically acceptable salt thereof, wherein R³ is H and eachR⁴ is H.

Another embodiment of the present invention is a compound of Formula IAor Formula IB:

wherein X, Y, Z, R³ and each R⁴ are as defined herein for Formula I,including all embodiments discussed herein. When referring to a compoundof Formula I, it is understood to also include a compound of Formula IAand IB without requiring specific reference.

In one embodiment, the invention also relates to each compound,individually, described in Examples 1 to 29 discussed herein (includingthe free bases or pharmaceutically acceptable salts thereof).

Another embodiment of the present invention is a method for orpreparation of a medicament for the treatment or prevention in a mammalof a condition selected from the group consisting of acute neurologicaland psychiatric disorders; stroke; cerebral ischemia; spinal cordtrauma; cognitive impairment, including mild cognitive impairment; headtrauma; perinatal hypoxia; cardiac arrest; hypoglycemic neuronal damage;dementia; Alzheimer's disease; Huntington's Chorea; amyotrophic lateralsclerosis; ocular damage; retinopathy; cognitive disorders; idiopathicand drug-induced Parkinson's disease; muscular spasms and disordersassociated with muscular spasticity including tremors; epilepsy;convulsions; migraine; urinary incontinence; substance tolerance;substance withdrawal; psychosis; schizophrenia; negative symptomsassociated with schizophrenia; autism, including autism spectrumdisorders; bipolar disorder; depression, including but not limited toMajor Depressive Disorder and treatment-resistant depression; cognitiveimpairment associated with depression; cognitive impairment associatedwith cancer therapy; anxiety; mood disorders; inflammatory disorders;sepsis; cirrhosis; cancer and/or tumors associated with immune responseescape; trigeminal neuralgia; hearing loss; tinnitus; maculardegeneration of the eye; emesis; brain edema; pain; tardive dyskinesia;sleep disorders; attention deficit/hyperactivity disorder; attentiondeficit disorder; disorders that comprise as a symptom of deficiency inattention and/or cognition; and conduct disorder; comprisingadministering a compound selected from a compound of Formula I, IA, orIB.

Another embodiment of the present invention is a method for orpreparation of a medicament for the treatment or prevention in a mammalof a condition selected from the group consisting of dementia; cognitivedeficit symptoms of Alzheimer's disease; attention deficit symptoms ofAlzheimer's disease; multi-infarct dementia, alcoholic dementia or otherdrug-related dementia, dementia associated with intracranial tumors orcerebral trauma, dementia associated with Huntington's disease orParkinson's disease, or AIDS-related dementia; delirium; amnesticdisorder; post-traumatic stress disorder; mental retardation; a learningdisorder (e.g., reading disorder, mathematics disorder, or a disorder ofwritten expression); attention-deficit/hyperactivity disorder;age-related cognitive decline; cognitive deficits associated withpsychoses; or cognitive deficits associated with schizophrenia,comprising administering a compound selected from a compound of FormulaI, IA, or IB.

Another embodiment of the present invention is a method for orpreparation of a medicament for the treatment or prevention in a mammalof a condition selected from the group consisting of acute neurologicaland psychiatric disorders; stroke; cerebral ischemia; spinal cordtrauma; cognitive impairment, including mild cognitive impairment; headtrauma; perinatal hypoxia; cardiac arrest; hypoglycemic neuronal damage;dementia; Alzheimer's disease; Huntington's Chorea; amyotrophic lateralsclerosis; ocular damage; retinopathy; cognitive disorders; idiopathicand drug-induced Parkinson's disease; muscular spasms and disordersassociated with muscular spasticity including tremors; epilepsy;convulsions; migraine; urinary incontinence; substance tolerance;substance withdrawal; psychosis; schizophrenia; negative symptomsassociated with schizophrenia; autism, including autism spectrumdisorders; bipolar disorder; depression, including but not limited toMajor Depressive Disorder and treatment-resistant depression; cognitiveimpairment associated with depression; cognitive impairment associatedwith cancer therapy; anxiety; mood disorders; inflammatory disorders;sepsis; cirrhosis; cancer and/or tumors associated with immune responseescape; trigeminal neuralgia; hearing loss; tinnitus; maculardegeneration of the eye; emesis; brain edema; pain; tardive dyskinesia;sleep disorders; attention deficit/hyperactivity disorder; attentiondeficit disorder; disorders that comprise as a symptom a deficiency inattention and/or cognition; and conduct disorder; comprisingadministering a compound of Formula I, IA, or IB.

Another embodiment of the present invention is a method for orpreparation of a medicament for the treatment or prevention in a mammalof a condition selected from the group consisting of dementia; cognitivedeficit symptoms of Alzheimer's disease; attention deficit symptoms ofAlzheimer's disease; multi-infarct dementia, alcoholic dementia or otherdrug-related dementia, dementia associated with intracranial tumors orcerebral trauma, dementia associated with Huntington's disease orParkinson's disease, or AIDS-related dementia; delirium; amnesticdisorder; post-traumatic stress disorder; mental retardation; a learningdisorder (e.g., reading disorder, mathematics disorder, or a disorder ofwritten expression); attention-deficit/hyperactivity disorder;age-related cognitive decline; cognitive deficits associated withpsychoses; or cognitive deficits associated with schizophrenia,comprising administering a compound of Formula I, IA, or IB.

Another embodiment of the present invention is a compound of Formula I,IA, or IB wherein X—Y—Z and carbon atoms to which they are attached makea five-membered ring

By using definitions of X, Y, and Z in Formula I, the following rings inTable A can be formed and fall within said definition:

TABLE A

Another embodiment of the pending invention is where X—Y—Z and carbonatoms to which they are attached make any of the five-membered rings asprovided in Table A; for example, the five-membered rings as provided inTable B:

TABLE B

Compounds of Formula I or compounds related thereto when R³ is H canform a Schiff base with pyridoxal-5-phosphate (also called PLP and/orvitamin B6) in the KAT II enzyme, to inhibit formation of kynurenicacid. Literature reports of other PLP-dependent enzymes (R. B. Silvermanet al., J. Am. Chem. Soc. 1998, 120, 2256-2267) also demonstrate that aninitially formed inhibitor-PLP Schiff base can undergo base-inducedtautomerization to an isomeric ketimine, which can further isomerize toan aromatized inhibitor-PLP adduct. Another embodiment of the presentinvention is a Schiff base, or the product of base-promotedisomerization thereof, formed between a compound of Formula I, IA, orIB, as defined herein, and pyridoxal-5-phosphate.

Another embodiment of the present invention is a Schiff base, or theproduct of base-promoted isomerization thereof, formed between acompound of Formula I, IA, or IB, as defined herein, andpyridoxal-5-phosphate, wherein said Schiff base is formed in vivo.

Prodrugs that have little or no pharmacological activity themselves can,when administered into or onto the body, be converted into compounds ofFormula I, IA, or IB having the desired activity. Such prodrugs arecompounds of Formula I, IA, or IB when R³ is other than H. For example,these compounds are where R³ is

ABBREVIATIONS AND DEFINITIONS

The term “alkyl” refers to a linear or branched-chain saturatedhydrocarbyl substituent (i.e., a substituent obtained from a hydrocarbonby removal of a hydrogen) containing from one to twenty carbon atoms; inone embodiment from one to twelve carbon atoms; in another embodiment,from one to ten carbon atoms; in another embodiment, from one to sixcarbon atoms; and in another embodiment, from one to three carbon atoms.Examples of such substituents include methyl, ethyl, propyl (includingn-propyl and isopropyl), butyl (including n-butyl, isobutyl, sec-butyland tert-butyl), pentyl, isoamyl, hexyl and the like.

“Alkenyl” refers to an aliphatic hydrocarbon having at least onecarbon-carbon double bond, including straight chain, branched chain orcyclic groups having at least one carbon-carbon double bond. In oneembodiment, the alkenyl group has 2 to 20 carbon atoms (whenever anumerical range; e.g., “2-20”, is stated herein, it means that thegroup, in this case the alkenyl group, may contain 2 carbon atoms, 3carbon atoms, etc. up to and including 20 carbon atoms). In anotherembodiment, it is a medium size alkenyl having 2 to 10 carbon atoms. Forexample, as used herein, the term “(C₂-C₆)alkenyl” means straight orbranched chain unsaturated radicals of 2 to 6 carbon atoms, including,but not limited to ethenyl, 1-propenyl, 2-propenyl(allyl), iso-propenyl,2-methyl-1-propenyl, 1-butenyl, 2-butenyl, and the like; optionallysubstituted by 1 to 5 suitable substituents as defined above such asfluoro, chloro, trifluoromethyl, (C₁-C₆)alkoxy, (C₆-C₁₀)aryloxy,trifluoromethoxy, difluoromethoxy or (C₁-C₆)alkyl. When the compounds ofthe invention contain a (C₂-C₆)alkenyl group, the compound may exist asthe pure E (entgegen) form, the pure Z (zusammen) form, or any mixturethereof.

“Alkynyl” refers to an aliphatic hydrocarbon having at least onecarbon-carbon triple bond, including straight chain, branched chain orcyclic groups having at least one carbon-carbon triple bond. In oneembodiment, the alkynyl group has 2 to 20 carbon atoms (whenever anumerical range; e.g., “2-20”, is stated herein, it means that thegroup, in this case the alkynyl group, may contain 2 carbon atoms, 3carbon atoms, etc. up to and including 20 carbon atoms). In anotherembodiment, it is a medium size alkynyl having 2 to 10 carbon atoms. Inanother embodiment, it is a lower alkynyl having 2 to 6 carbon atoms.For example, as used herein, the term “(C₂-C₆)alkynyl” is used herein tomean straight or branched hydrocarbon chain alkynyl radical as definedabove having 2 to 6 carbon atoms and one triple bond.

The term “cycloalkyl” refers to a carbocyclic substituent obtained byremoving a hydrogen from a saturated carbocyclic molecule and havingthree to fourteen carbon atoms. In one embodiment, a cycloalkylsubstituent has three to ten carbon atoms. Cycloalkyl may be a singlering, which typically contains from 3 to 6 ring atoms. Examples ofcycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.Alternatively, cycloalkyl may be 2 or 3 rings fused together, such asbicyclo[4.2.0]octane and decalinyl.

The term “cycloalkyl” also includes substituents that are fused to aC₆-C₁₀ aromatic ring or to a 5-10-membered heteroaromatic ring, whereina group having such a fused cycloalkyl group as a substituent is boundto a carbon atom of the cycloalkyl group. When such a fused cycloalkylgroup is substituted with one or more substituents, the one or moresubstituents, unless otherwise specified, are each bound to a carbonatom of the cycloalkyl group. The fused C₆-C₁₀ aromatic ring or5-10-membered heteroaromatic ring may be optionally substituted withhalogen, C₁-C₆ alkyl, C₃-C₁₀ cycloalkyl, or ═O.

The term “aryl” refers to an aromatic substituent containing one ring ortwo or three fused rings. The aryl substituent may have six to eighteencarbon atoms. As an example, the aryl substituent may have six tofourteen carbon atoms. The term “aryl” may refer to substituents such asphenyl, naphthyl and anthracenyl. The term “aryl” also includessubstituents such as phenyl, naphthyl and anthracenyl that are fused toa C₄-C₁₀ carbocyclic ring, such as a C₅- or a C₆-carbocyclic ring, or toa 4-10-membered heterocyclic ring, wherein a group having such a fusedaryl group as a substituent is bound to an aromatic carbon of the arylgroup. When such a fused aryl group is substituted with one or moresubstituents, the one or more substituents, unless otherwise specified,are each bound to an aromatic carbon of the fused aryl group. The fusedC₄-C₁₀ carbocyclic or 4-10-membered heterocyclic ring may be optionallysubstituted with halogen, C₁-C₆ alkyl, C₃-C₁₀ cycloalkyl, or ═O.Examples of aryl groups include accordingly phenyl, naphthalenyl,tetrahydronaphthalenyl (also known as “tetralinyl”), indenyl,isoindenyl, indanyl, anthracenyl, phenanthrenyl, and benzonaphthenyl(also known as “phenalenyl”).

The term “aralkyl” or “arylalkyl” refers to an alkyl substituent, asdefined herein, substituted by an aryl substituent, as defined herein.Aralkyl substituents may have from seven to 24 carbon atoms. Examples ofaralkyl groups include benzyl (i.e., phenylmethyl), phenylethyl,indenylmethyl, and naphthalenylethyl.

In some instances, the number of carbon atoms in a hydrocarbylsubstituent (i.e., alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, etc.)is indicated by the prefix “C_(X)-C_(y)” or “C_(x-y),” wherein x is theminimum and y is the maximum number of carbon atoms in the substituent.Thus, for example, “C₁-C₆ alkyl and “C₁₋₆ alkyl” both refer to an alkylsubstituent containing from 1 to 6 carbon atoms. Illustrating further,C₃-C₆ cycloalkyl and C₃₋₆ cycloalkyl refer to saturated cycloalkylcontaining from 3 to 6 carbon ring atoms.

In some instances, the number of atoms in a cyclic substituentcontaining one or more heteroatoms (i.e., heteroaryl orheterocycloalkyl) is indicated by the prefix “x-y-membered”, wherein xis the minimum and y is the maximum number of atoms forming the cyclicmoiety of the substituent. Thus, for example, 5-8-memberedheterocycloalkyl refers to a heterocycloalkyl containing from 5 to 8atoms, including one or more heteroatoms, in the cyclic moiety of theheterocycloalkyl.

The term “hydroxy” or “hydroxyl” refers to —OH. When used in combinationwith another term(s), the prefix “hydroxy” indicates that thesubstituent to which the prefix is attached is substituted with one ormore hydroxy substituents. Compounds bearing a carbon to which one ormore hydroxy substituents are attached include, for example, alcohols,enols and phenol.

The term “hydroxyalkyl” refers to an alkyl that is substituted with atleast one hydroxy substituent. Examples of hydroxyalkyl includehydroxymethyl, hydroxyethyl, hydroxypropyl and hydroxybutyl.

The term “cyano” (also referred to as “nitrile”) means CN.

The term “carbonyl” means C(O) or C═O.

The term “amino” refers to NH₂.

The term “alkylamino” refers to an amino group, wherein at least onealkyl chain is bonded to the amino nitrogen in place of a hydrogen atom.Examples of alkylamino substituents include monoalkylamino such asmethylamino (exemplified by the formula NH(CH₃)), and dialkylamino suchas dimethylamino (exemplified by the formula —N(CH₃)₂).

The term “halogen” refers to fluorine (which may be depicted as F),chlorine (which may be depicted as Cl), bromine (which may be depictedas Br), or iodine (which may be depicted as I). In one embodiment, thehalogen is chlorine. In another embodiment, the halogen is fluorine. Inanother embodiment, the halogen is bromine.

The prefix “halo” indicates that the substituent to which the prefix isattached is substituted with one or more independently selected halogensubstituents. For example, haloalkyl refers to an alkyl that issubstituted with at least one halogen substituent. Where more than onehydrogen is replaced with halogens, the halogens may be identical ordifferent. Examples of haloalkyls include chloromethyl, dichloromethyl,difluorochloromethyl, dichlorofluoromethyl, trichloromethyl,1-bromoethyl, fluoromethyl, difluoromethyl, trifluoromethyl,2,2,2-trifluoroethyl, difluoroethyl, pentafluoroethyl, difluoropropyl,dichloropropyl, and heptafluoropropyl. Illustrating further,“haloalkoxy” refers to an alkoxy that is substituted with at least onehalogen substituent. Examples of haloalkoxy substituents includechloromethoxy, 1-bromoethoxy, fluoromethoxy, difluoromethoxy,trifluoromethoxy (also known as “perfluoromethyloxy”), and2,2,2-trifluoroethoxy. It should be recognized that if a substituent issubstituted by more than one halogen substituent, those halogensubstituents may be identical or different (unless otherwise stated).

The term “oxo” refers to ═O.

The term “alkoxy” refers to an alkyl linked to an oxygen, which may alsobe represented as —OR, wherein the R represents the alkyl group.Examples of alkoxy include methoxy, ethoxy, propoxy and butoxy.

The term “cycloalkyloxy” refers to a cycloalkyl linked to an oxygen,which may also be represented as —OR, wherein the R represents thecycloalkyl group. Examples of cycloalkyloxy include cyclopropyloxy,cyclobutyloxy, and cyclopentyloxy.

The term “heterocycloalkyl” refers to a substituent obtained by removinga hydrogen from a saturated or partially saturated ring structurecontaining a total of 4 to 14 ring atoms. At least one of the ring atomsis a heteroatom usually selected from oxygen, nitrogen, or sulfur. Aheterocycloalkyl alternatively may comprise 2 or 3 rings fused together,wherein at least one such ring contains a heteroatom as a ring atom(i.e., nitrogen, oxygen, or sulfur). In a group that has aheterocycloalkyl substituent, the ring atom of the heterocycloalkylsubstituent that is bound to the group may be the at least oneheteroatom, or it may be a ring carbon atom, where the ring carbon atommay be in the same ring as the at least one heteroatom or where the ringcarbon atom may be in a different ring from the at least one heteroatom.Similarly, if the heterocycloalkyl substituent is in turn substitutedwith a group or substituent, the group or substituent may be bound tothe at least one heteroatom, or it may be bound to a ring carbon atom,where the ring carbon atom may be in the same ring as the at least oneheteroatom or where the ring carbon atom may be in a different ring fromthe at least one heteroatom.

The term “heterocycloalkyl” also includes substituents that are fused toa C₆-C₁₀ aromatic ring or to a 5-10-membered heteroaromatic ring,wherein a group having such a fused heterocycloalkyl group as asubstituent is bound to a heteroatom of the heterocycloalkyl group or toa carbon atom of the heterocycloalkyl group. When such a fusedheterocycloalkyl group is substituted with one or more substituents, theone or more substituents, unless otherwise specified, are each bound toa heteroatom of the heterocycloalkyl group or to a carbon atom of theheterocycloalkyl group. The fused C₆-C₁₀ aromatic ring or 5-10-memberedheteroaromatic ring may be optionally substituted with halogen, C₁-C₆alkyl, C₃-C₁₀ cycloalkyl, C₁-C₆ alkoxy, or ═O.

The term “heterocycloalkyloxy” refers to a heterocycloalkyl linked to anoxygen, which may also be represented as —OR, wherein the R representsthe heterocycloalkyl group. Examples of heterocycloalkyloxy includeoxetanyloxy (such as oxetan-3-yloxy), tetrahydrofuranyloxy (such astetrahydrofuran-3-yloxy), and tetrahydropyranyloxy (such astetrahydro-2H-pyran-4-yloxy or tetrahydro-2H-pyran-3-yloxy).

The term “heteroaryl” refers to an aromatic ring structure containingfrom 5 to 14 ring atoms in which at least one of the ring atoms is aheteroatom (i.e., oxygen, nitrogen, or sulfur), with the remaining ringatoms being independently selected from the group consisting of carbon,oxygen, nitrogen, and sulfur. A heteroaryl may be a single ring or 2 or3 fused rings.

Examples of heteroaryl substituents include 6-membered ring substituentssuch as pyridyl, pyrazyl, pyrimidinyl, and pyridazinyl; 5-membered ringsubstituents such as triazolyl, imidazolyl, furanyl, thiophenyl,pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, 1,2,3-, 1,2,4-, 1,2,5-, or1,3,4-oxadiazolyl and isothiazolyl; 6-/5-membered fused ringsubstituents such as benzothiofuranyl, isobenzothiofuranyl,benzisoxazolyl, benzoxazolyl and purinyl; and 6-/6-membered fused ringssuch as quinolinyl, isoquinolinyl, cinnolinyl, quinazolinyl, and1,4-benzoxazinyl. In a group that has a heteroaryl substituent, the ringatom of the heteroaryl substituent that is bound to the group may be theat least one heteroatom, or it may be a ring carbon atom, where the ringcarbon atom may be in the same ring as the at least one heteroatom orwhere the ring carbon atom may be in a different ring from the at leastone heteroatom. Similarly, if the heteroaryl substituent is in turnsubstituted with a group or substituent, the group or substituent may bebound to the at least one heteroatom, or it may be bound to a ringcarbon atom, where the ring carbon atom may be in the same ring as theat least one heteroatom or where the ring carbon atom may be in adifferent ring from the at least one heteroatom. The term “heteroaryl”also includes pyridyl N-oxides and groups containing a pyridine N-oxidering.

Examples of single ring heteroaryls include furanyl, thiophenyl (alsoknown as “thiofuranyl”), pyrrolyl, imidazolyl, pyrazolyl, triazolyl,tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, thiadiazolyl,oxadiazolyl [including 1,2,4-oxadiazolyl (also known as “azoximyl”),1,2,5-oxadiazolyl (also known as “furazanyl”), or 1,3,4-oxadiazolyl],oxatriazolyl (including 1,2,3,4-oxatriazolyl or 1,2,3,5-oxatriazolyl),pyridinyl (also known as “azinyl”), diazinyl [including pyridazinyl(also known as “1,2-diazinyl”), pyrimidinyl (also known as“1,3-diazinyl” or “pyrimidyl”), or pyrazinyl (also known as“1,4-diazinyl”)], and triazinyl [including s-triazinyl (also known as“1,3,5-triazinyl”), as-triazinyl (also known 1,2,4-triazinyl), andv-triazinyl (also known as “1,2,3-triazinyl”)].

Examples of 2-fused-ring heteroaryls include indolizinyl, pyrindinyl,purinyl, naphthyridinyl, pyridopyridinyl (includingpyrido[3,4-b]-pyridinyl, pyrido[3,2-b]pyridinyl, orpyrido[4,3-b]pyridinyl), and pteridinyl, indolyl, isoindolyl,isoindazolyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzoxazolyl,indoxazinyl, anthranilyl, benzoxadiazolyl, benzofuranyl,isobenzofuranyl, benzothienyl, isobenzothienyl, benzothiazolyl,benzothiadiazolyl, benzimidazolyl, benzotriazolyl, benzoxazinyl, andbenzisoxazinyl.

Examples of 3-fused-ring heteroaryls or heterocycloalkyls include5,6-dihydro-4H-imidazo[4,5,1-ij]quinoline,4,5-dihydroimidazo[4,5,1-hi]indole,4,5,6,7-tetrahydroimidazo[4,5,1-jk][1]benzazepine, and dibenzofuranyl.

Other examples of fused ring heteroaryls include benzo-fused heteroarylssuch as indolyl, isoindolyl (also known as “isobenzazolyl” or“pseudoisoindolyl”), benzazinyl [including quinolinyl (also known as“1-benzazinyl”) or isoquinolinyl (also known as “2-benzazinyl”)],phthalazinyl, quinoxalinyl, quinazolinyl, benzodiazinyl [includingcinnolinyl (also known as “1,2-benzodiazinyl”) or quinazolinyl (alsoknown as “1,3-benzodiazinyl”)], benzoxazolyl, indoxazinyl (also known as“benzisoxazolyl”), benzoxadiazolyl, benzofuranyl (also known as“coumaronyl”), isobenzofuranyl, benzothienyl (also known as“benzothiophenyl,” “thionaphthenyl,” or “benzothiofuranyl”),isobenzothienyl (also known as “isobenzothiophenyl,”“isothianaphthenyl,” or “isobenzothiofuranyl”), benzothiazolyl,benzothiadiazolyl, benzimidazolyl, benzotriazolyl, benzoxazinyl,benzisoxazinyl (including 1,2-benzisoxazinyl or 1,4-benzisoxazinyl),carbazolyl, and acridinyl.

The term “heteroaryl” also includes substituents such as pyridyl andquinolinyl that are fused to a C₄-C₁₀ carbocyclic ring, such as a C₅ ora C₆ carbocyclic ring, or to a 4-10-membered heterocyclic ring, whereina group having such a fused aryl group as a substituent is bound to anaromatic carbon of the heteroaryl group or to a heteroatom of theheteroaryl group. When such a fused heteroaryl group is substituted withone or more substituents, the one or more substituents, unless otherwisespecified, are each bound to an aromatic carbon of the heteroaryl groupor to a heteroatom of the heteroaryl group. The fused C₄-C₁₀ carbocyclicor 4-10-membered heterocyclic ring may be optionally substituted withhalogen, C₁-C₆ alkyl, C₃-C₁₀ cycloalkyl, or ═O.

Additional examples of heteroaryls and heterocycloalkyls include:3-1H-benzimidazol-2-one, (1-substituted)-2-oxo-benzimidazol-3-yl,2-tetrahydrofuranyl, 3-tetrahydrofuranyl, 2-tetrahydropyranyl,3-tetrahydropyranyl, 4-tetrahydropyranyl, [1,3]-dioxalanyl,[1,3]-dithiolanyl, [1,3]-dioxanyl, 2-tetrahydrothiophenyl,3-tetrahydrothiophenyl, 2-morpholinyl, 3-morpholinyl, 4-morpholinyl,2-thiomorpholinyl, 3-thiomorpholinyl, 4-thiomorpholinyl, 1-pyrrolidinyl,2-pyrrolidinyl, 3-pyrrolidinyl, 1-piperazinyl, 2-piperazinyl,1-piperidinyl, 2-piperidinyl, 3-piperidinyl, 4-piperidinyl,4-thiazolidinyl, 2H-imidazol-2-one, 1-phthalimidinyl, benzoxanyl,benzo[1,3]dioxine, benzo[1,4]dioxine, benzopyrrolidinyl,benzopiperidinyl, benzoxolanyl, benzothiolanyl,4,5,6,7-tetrahydropyrazol[1,5-a]pyridine, benzothianyl, pyrrolidinyl,dihydrofuranyl, tetrahydrothienyl, dihydropyranyl,tetrahydrothiopyranyl, piperidino, morpholino, thiomorpholino,thioxanyl, piperazinyl, azetidinyl, oxetanyl, thietanyl,homopiperidinyl, oxepanyl, thiepanyl, oxazepinyl, diazepinyl,thiazepinyl, 1,2,3,6-tetrahydropyridinyl, 2-pyrrolinyl, 3-pyrrolinyl,indolinyl, 2H-pyranyl, 4H-pyranyl, dioxanyl, 1,3-dioxolanyl,pyrazolinyl, dithianyl, dithiolanyl, dihydropyranyl, dihydrothienyl,dihydrofuranyl, pyrazolidinyl, imidazolinyl, imidazolidinyl,3-azabicyclo[3.1.0]hexanyl, 3-azabicyclo[4.1.0]heptanyl, 3H-indolyl,quinolizinyl, pyridinyl, imidazolyl, pyrimidinyl, pyrazolyl, triazolyl,pyrazinyl, tetrazolyl, furyl, thienyl, isoxazolyl, thiazolyl, oxazolyl,isothiazolyl, pyrrolyl, quinolinyl, isoquinolinyl, indolyl,benzimidazolyl, benzofuranyl, cinnolinyl, indazolyl, indolizinyl,phthalazinyl, pyridazinyl, triazinyl, isoindolyl, pteridinyl, purinyl,oxadiazolyl, thiadiazolyl, furazanyl, benzofurazanyl, benzothiophenyl,benzothiazolyl, benzoxazolyl, quinazolinyl, quinoxalinyl,naphthyridinyl, and furopyridinyl. The foregoing groups, as derived fromthe groups listed above, may be C-attached or N-attached where such ispossible. For instance, a group derived from pyrrole may be pyrrol-1-yl(N-attached) or pyrrol-3-yl (C-attached). Further, a group derived fromimidazole may be imidazol-1-yl (N-attached) or imidazol-2-yl(C-attached).

If a substituent is described as being “substituted,” a non-hydrogensubstituent is in the place of a hydrogen attached to a carbon, oxygen,sulfur or nitrogen of the substituent. Thus, for example, a substitutedalkyl substituent is an alkyl substituent wherein at least onenon-hydrogen substituent is in the place of a hydrogen substituent onthe alkyl substituent. To illustrate, monofluoroalkyl is alkylsubstituted with a fluoro substituent, and difluoroalkyl is alkylsubstituted with two fluoro substituents. It should be recognized thatif there is more than one substitution on a substituent, eachnon-hydrogen substituent may be identical or different (unless otherwisestated).

If a substituent is described such that it “may be substituted” or“optionally substituted,” the substituent may be either substituted ornot substituted. If a carbon of a substituent is described such that itmay be substituted or is optionally substituted with one or more of alist of substituents, one or more of the hydrogens on the carbon (to theextent there are any) may separately and/or together be replaced with anindependently selected optional substituent. If a nitrogen of asubstituent is described as being optionally substituted with one ormore of a list of substituents, one or more of the hydrogens on thenitrogen (to the extent there are any) may each be replaced with anindependently selected optional substituent. One exemplary substituentmay be depicted as —NR′R″, wherein R′ and R″ together with the nitrogenatom to which they are attached, may form a heterocyclic ring. Theheterocyclic ring formed from R′ and R″ together with the nitrogen atomto which they are attached may be partially or fully saturated. In oneembodiment, the heterocyclic ring consists of 4 to 7 atoms. In anotherembodiment, the heterocyclic ring is selected from the group consistingof azepinyl, piperidinyl, pyrrolidinyl, morpholino, thiomorpholino,piperazinyl, and azetidinyl.

If a group of substituents are collectively described as beingoptionally substituted by one or more of a list of substituents, thegroup may include: (1) unsubstitutable substituents, (2) substitutablesubstituents that are not substituted by the optional substituents,and/or (3) substitutable substituents that are substituted by one ormore of the optional substituents.

If a substituent is described as being optionally substituted with up toa particular number of non-hydrogen substituents, that substituent maybe either (1) not substituted; or (2) substituted by up to thatparticular number of non-hydrogen substituents or by up to the maximumnumber of substitutable positions on the substituent, whichever is less.Thus, for example, if a substituent is described as a heteroaryloptionally substituted with up to 3 non-hydrogen substituents, then anyheteroaryl with less than 3 substitutable positions would be optionallysubstituted by up to only as many non-hydrogen substituents as theheteroaryl has substitutable positions. To illustrate, tetrazolyl (whichhas only one substitutable position) would be optionally substitutedwith up to one non-hydrogen substituent. To illustrate further, if anamino nitrogen is described as being optionally substituted with up to 2non-hydrogen substituents, then the nitrogen will be optionallysubstituted with up to 2 non-hydrogen substituents if the amino nitrogenis a primary nitrogen, whereas the amino nitrogen will be optionallysubstituted with up to only 1 non-hydrogen substituent if the aminonitrogen is a secondary nitrogen.

A prefix attached to a multi-moiety substituent only applies to thefirst moiety. To illustrate, the term “alkylcycloalkyl” contains twomoieties: alkyl and cycloalkyl. Thus, a C₁-C₆ prefix on C₁-C₆alkylcycloalkyl means that the alkyl moiety of the alkylcycloalkylcontains from 1 to 6 carbon atoms; the C₁-C₆ prefix does not describethe cycloalkyl moiety. To illustrate further, the prefix “halo” onhaloalkoxyalkyl indicates that only the alkoxy moiety of the alkoxyalkylsubstituent is substituted with one or more halogen substituents. If thehalogen substitution only occurs on the alkyl moiety, the substituentwould be described as “alkoxyhaloalkyl.” If the halogen substitutionoccurs on both the alkyl moiety and the alkoxy moiety, the substituentwould be described as “haloalkoxyhaloalkyl.”

If substituents are described as being “independently selected” from agroup, each substituent is selected independent of the other. Eachsubstituent therefore may be identical to or different from the othersubstituent(s).

As used herein the term “Formula I” may be referred to as “a compound ofthe invention” or as “compounds of the invention.” Such terms are alsodefined to include all forms of the compound of Formula I, includinghydrates, solvates, isomers, crystalline and non-crystalline forms,isomorphs, polymorphs, and metabolites thereof.

The following abbreviations are used herein:

brine: saturated aqueous sodium chloride solutionDCC: 1,3-dicyclohexylcarbodiimideEDCI: 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochlorideEtOAc: ethyl acetateHBTU: O-benzotriazol-1-yl-N,N,N′,N′-tetramethyluroniumhexafluorophosphateHMBC: heteronuclear multiple bond correlationmin: minutesNOE: nuclear Overhauser effectpsi: pounds per square inchRT: room temperatureSEM: [2-(trimethylsilyl)ethoxy]methyl

Isomers

When an asymmetric center is present in a compound of Formula I,hereinafter referred to as the compound of the invention, the compoundmay exist in the form of optical isomers (enantiomers). In oneembodiment, the present invention comprises enantiomers and mixtures,including racemic mixtures of the compounds of Formula I. In anotherembodiment, for compounds of Formula I that contain more than oneasymmetric center, the present invention comprises diastereomeric forms(individual diastereomers and mixtures thereof) of compounds. When acompound of Formula I contains an alkenyl group or moiety, geometricisomers may arise.

Tautomeric Forms

The present invention comprises the tautomeric forms of compounds ofFormula I. Where structural isomers are interconvertible via a lowenergy barrier, tautomeric isomerism (‘tautomerism’) can occur. This cantake the form of proton tautomerism in compounds of Formula Icontaining, for example, an imino, keto, or oxime group, or so-calledvalence tautomerism in compounds which contain an aromatic moiety. Itfollows that a single compound may exhibit more than one type ofisomerism. The various ratios of the tautomers in solid and liquid formis dependent on the various substituents on the molecule as well as theparticular crystallization technique used to isolate a compound.

Salts

The compounds of this invention may be used in the form of salts derivedfrom inorganic or organic acids. Depending on the particular compound, asalt of the compound may be advantageous due to one or more of thesalt's physical properties, such as enhanced pharmaceutical stability indiffering temperatures and humidities, or a desirable solubility inwater or oil. In some instances, a salt of a compound also may be usedas an aid in the isolation, purification, and/or resolution of thecompound.

Where a salt is intended to be administered to a patient (as opposed to,for example, being used in an in vitro context), the salt preferably ispharmaceutically acceptable. The term “pharmaceutically acceptable salt”refers to a salt prepared by combining a compound of Formula I with anacid whose anion, or a base whose cation, is generally consideredsuitable for human consumption. Pharmaceutically acceptable salts areparticularly useful as products of the methods of the present inventionbecause of their greater aqueous solubility relative to the parentcompound. For use in medicine, the salts of the compounds of thisinvention are non-toxic “pharmaceutically acceptable salts.” Saltsencompassed within the term “pharmaceutically acceptable salts” refer tonon-toxic salts of the compounds of this invention which are generallyprepared by reacting the free base with a suitable organic or inorganicacid.

Suitable pharmaceutically acceptable acid addition salts of thecompounds of the present invention when possible include those derivedfrom inorganic acids, such as hydrochloric, hydrobromic, hydrofluoric,boric, fluoroboric, phosphoric, metaphosphoric, nitric, carbonic,sulfonic, and sulfuric acids, and organic acids such as acetic,benzenesulfonic, benzoic, citric, ethanesulfonic, fumaric, gluconic,glycolic, isothionic, lactic, lactobionic, maleic, malic,methanesulfonic, trifluoromethanesulfonic, succinic, toluenesulfonic,tartaric, and trifluoroacetic acids. Suitable organic acids generallyinclude, for example, aliphatic, cycloaliphatic, aromatic, araliphatic,heterocyclic, carboxylic, and sulfonic classes of organic acids.

Specific examples of suitable organic acids include acetate,trifluoroacetate, formate, propionate, succinate, glycolate, gluconate,digluconate, lactate, malate, tartrate, citrate, ascorbate, glucuronate,maleate, fumarate, pyruvate, aspartate, glutamate, benzoate,anthranilate, stearate, salicylate, p-hydroxybenzoate, phenylacetate,mandelate, embonate (pamoate), methanesulfonate, ethanesulfonate,benzenesulfonate, pantothenate, toluenesulfonate,2-hydroxyethanesulfonate, sulfanilate, cyclohexylaminosulfonate,β-hydroxybutyrate, galactarate, galacturonate, adipate, alginate,butyrate, camphorate, camphorsulfonate, cyclopentanepropionate,dodecylsulfate, glycoheptanoate, glycerophosphate, heptanoate,hexanoate, nicotinate, 2-naphthalesulfonate, oxalate, palmoate,pectinate, 3-phenylpropionate, picrate, pivalate, thiocyanate, andundecanoate.

Furthermore, where the compounds of the invention carry an acidicmoiety, suitable pharmaceutically acceptable salts thereof may includealkali metal salts, i.e., sodium or potassium salts; alkaline earthmetal salts, e.g., calcium or magnesium salts; and salts formed withsuitable organic ligands, e.g., quaternary ammonium salts. In anotherembodiment, base salts are formed from bases which form non-toxic salts,including aluminum, arginine, benzathine, choline, diethylamine,diethanolamine, glycine, lysine, meglumine, ethanolamine, tromethamineand zinc salts.

Organic salts may be made from secondary, tertiary or quaternary aminesalts, such as tromethamine, diethylamine, N,N′-dibenzylethylenediamine,chloroprocaine, choline, diethanolamine, ethylenediamine, meglumine(N-methylglucamine), and procaine. Basic nitrogen-containing groups maybe quaternized with agents such as lower alkyl (C₁-C₆) halides (e.g.,methyl, ethyl, propyl, and butyl chlorides, bromides, and iodides),dialkyl sulfates (i.e., dimethyl, diethyl, dibutyl, and diamylsulfates), long chain halides (i.e., decyl, lauryl, myristyl, andstearyl chlorides, bromides, and iodides), arylalkyl halides (i.e.,benzyl and phenethyl bromides), and others.

In one embodiment, hemisalts of acids and bases may also be formed, forexample, hemisulphate and hemicalcium salts.

Isotopes

The present invention also includes isotopically labeled compounds,which are identical to those recited in Formula I, but for the fact thatone or more atoms are replaced by an atom having an atomic mass or massnumber different from the atomic mass or mass number usually found innature. Examples of isotopes that can be incorporated into compounds ofthe present invention include isotopes of hydrogen, carbon, nitrogen,oxygen, phosphorous, sulfur, fluorine and chlorine, such as ²H, ³H, ¹³C,¹¹C, ¹⁴C, ¹⁵N, ¹⁸O, ¹⁷O, ³²P, ³⁵S, ¹⁸F, and ³⁶Cl, respectively.Compounds of the present invention, prodrugs thereof, andpharmaceutically acceptable salts of said compounds or of said prodrugswhich contain the aforementioned isotopes and/or other isotopes of otheratoms are within the scope of this invention. Certain isotopicallylabeled compounds of the present invention, for example those into whichradioactive isotopes such as ³H and ¹⁴C are incorporated, are useful indrug and/or substrate tissue distribution assays. Tritiated, i.e., ³H,and carbon-14, i.e., ¹⁴C, isotopes are particularly preferred for theirease of preparation and detectability. Further, substitution withheavier isotopes such as deuterium, i.e., ²H, can afford certaintherapeutic advantages resulting from greater metabolic stability, forexample increased in vivo half-life or reduced dosage requirements and,hence, may be preferred in some circumstances. Isotopically labeledcompounds of Formula I of this invention and prodrugs thereof cangenerally be prepared by carrying out the procedures disclosed in theSchemes and/or in the Examples and Preparations below, by substituting areadily available isotopically labeled reagent for a non-isotopicallylabeled reagent.

The invention also relates to prodrugs of the compounds of Formula I.Thus certain derivatives of compounds of Formula I which may have littleor no pharmacological activity themselves can, when administered into oronto the body, be converted into compounds of Formula I having thedesired activity, for example, by hydrolytic cleavage. Such derivativesare referred to as “prodrugs”. Further information on the use ofprodrugs may be found in Pro-drugs as Novel Delivery Systems, Vol. 14,ACS Symposium Series (T. Higuchi and W. Stella) and BioreversibleCarriers in Drug Design, Pergamon Press, 1987 (Ed. E. B. Roche, AmericanPharmaceutical Association).

Prodrugs in accordance with the invention can, for example, be producedby replacing appropriate functionalities present in the compounds ofFormula I with certain moieties known to those skilled in the art as‘pro-moieties’ as described, for example, in Design of Prodrugs by H.Bundgaard (Elsevier, 1985).

Some non-limiting examples of prodrugs in accordance with the inventioninclude:

-   -   (i) where the compound of Formula I contains a carboxylic acid        functionality which is functionalized into a suitably        metabolically labile group (esters, carbamates, etc.) on the        compound of Formula I;    -   (ii) where the compound of Formula I contains an alcohol        functionality which is functionalized into a suitably        metabolically labile group (esters, carbonates, carbamates,        acetals, ketals, etc.) on the compound of Formula I; and    -   (iii) where the compound of Formula I contains a primary or        secondary amino functionality, or an amide which is        functionalized into a suitably metabolically labile group, e.g.,        a hydrolyzable group (amides, carbamates, ureas, etc.) on the        compound of Formula I.

Further examples of replacement groups in accordance with the foregoingexamples and examples of other prodrug types may be found in theaforementioned references.

Moreover, certain compounds of Formula I may themselves act as prodrugsof other compounds of Formula I.

Administration and Dosing

Typically, a compound of the invention is administered in an amounteffective to treat a condition as described herein. The compounds of theinvention are administered by any suitable route in the form of apharmaceutical composition adapted to such a route, and in a doseeffective for the treatment intended. Therapeutically effective doses ofthe compounds required to treat the progress of the medical conditionare readily ascertained by one of ordinary skill in the art usingpreclinical and clinical approaches familiar to the medicinal arts.

The compounds of the invention may be administered orally. Oraladministration may involve swallowing, so that the compound enters thegastrointestinal tract, or buccal or sublingual administration may beemployed by which the compound enters the bloodstream directly from themouth.

In another embodiment, the compounds of the invention may also beadministered directly into the bloodstream, into muscle, or into aninternal organ. Suitable means for parenteral administration includeintravenous, intraarterial, intraperitoneal, intrathecal,intraventricular, intraurethral, intrasternal, intracranial,intramuscular and subcutaneous. Suitable devices for parenteraladministration include needle (including microneedle) injectors,needle-free injectors and infusion techniques.

In another embodiment, the compounds of the invention may also beadministered topically to the skin or mucosa, that is, dermally ortransdermally. In another embodiment, the compounds of the invention canalso be administered intranasally or by inhalation. In anotherembodiment, the compounds of the invention may be administered rectallyor vaginally. In another embodiment, the compounds of the invention mayalso be administered directly to the eye or ear.

The dosage regimen for the compounds and/or compositions containing thecompounds is based on a variety of factors, including the type, age,weight, sex and medical condition of the patient; the severity of thecondition; the route of administration; and the activity of theparticular compound employed. Thus the dosage regimen may vary widely.Dosage levels of the order from about 0.01 mg to about 100 mg perkilogram of body weight per day are useful in the treatment of theabove-indicated conditions. In one embodiment, the total daily dose of acompound of the invention (administered in single or divided doses) istypically from about 0.01 to about 100 mg/kg. In another embodiment,total daily dose of the compound of the invention is from about 0.1 toabout 50 mg/kg, and in another embodiment, from about 0.5 to about 30mg/kg (i.e., mg compound of the invention per kg body weight). In oneembodiment, dosing is from 0.01 to 10 mg/kg/day. In another embodiment,dosing is from 0.1 to 1.0 mg/kg/day. Dosage unit compositions maycontain such amounts or submultiples thereof to make up the daily dose.In many instances, the administration of the compound will be repeated aplurality of times in a day (typically no greater than 4 times).Multiple doses per day typically may be used to increase the total dailydose, if desired.

For oral administration, the compositions may be provided in the form oftablets containing 0.01, 0.05, 0.1, 0.5, 1.0, 2.5, 5.0, 10.0, 15.0,25.0, 50.0, 75.0, 100, 125, 150, 175, 200, 250 and 500 milligrams of theactive ingredient for the symptomatic adjustment of the dosage to thepatient. A medicament typically contains from about 0.01 mg to about 500mg of the active ingredient, or in another embodiment, from about 1 mgto about 100 mg of active ingredient. Intravenously, doses may rangefrom about 0.01 to about 10 mg/kg/minute during a constant rateinfusion.

Suitable subjects according to the present invention include mammaliansubjects. Mammals according to the present invention include, but arenot limited to, canine, feline, bovine, caprine, equine, ovine, porcine,rodents, lagomorphs, primates, and the like, and encompass mammals inutero. In one embodiment, humans are suitable subjects. Human subjectsmay be of either gender and at any stage of development.

Use in the Preparation of a Medicament

In another embodiment, the invention comprises the use of one or morecompounds of the invention for the preparation of a medicament for thetreatment of the conditions recited herein.

Pharmaceutical Compositions

For the treatment of the conditions referred to herein, the compound ofthe invention can be administered as compound per se. Alternatively,pharmaceutically acceptable salts are suitable for medical applicationsbecause of their greater aqueous solubility relative to the parentcompound.

In another embodiment, the present invention comprises pharmaceuticalcompositions. Such pharmaceutical compositions comprise a compound ofthe invention presented with a pharmaceutically acceptable carrier. Thecarrier can be a solid, a liquid, or both, and may be formulated withthe compound as a unit-dose composition, for example, a tablet, whichcan contain from 0.05% to 95% by weight of the active compounds. Acompound of the invention may be coupled with suitable polymers astargetable drug carriers. Other pharmacologically active substances canalso be present.

The compounds of the present invention may be administered by anysuitable route, preferably in the form of a pharmaceutical compositionadapted to such a route, and in a dose effective for the treatmentintended. The active compounds and compositions, for example, may beadministered orally, rectally, parenterally, or topically.

Oral administration of a solid dose form may be, for example, presentedin discrete units, such as hard or soft capsules, pills, cachets,lozenges, or tablets, each containing a predetermined amount of at leastone compound of the present invention. In another embodiment, the oraladministration may be in a powder or granule form. In anotherembodiment, the oral dose form is sub-lingual, such as, for example, alozenge. In such solid dosage forms, the compounds of Formula I areordinarily combined with one or more adjuvants. Such capsules or tabletsmay contain a controlled-release formulation. In the case of capsules,tablets, and pills, the dosage forms also may comprise buffering agentsor may be prepared with enteric coatings.

In another embodiment, oral administration may be in a liquid dose form.Liquid dosage forms for oral administration include, for example,pharmaceutically acceptable emulsions, solutions, suspensions, syrups,and elixirs containing inert diluents commonly used in the art (i.e.,water). Such compositions also may comprise adjuvants, such as wetting,emulsifying, suspending, flavoring (e.g., sweetening), and/or perfumingagents.

In another embodiment, the present invention comprises a parenteral doseform. “Parenteral administration” includes, for example, subcutaneousinjections, intravenous injections, intraperitoneally, intramuscularinjections, intrasternal injections, and infusion. Injectablepreparations (i.e., sterile injectable aqueous or oleaginoussuspensions) may be formulated according to the known art using suitabledispersing, wetting agents, and/or suspending agents.

In another embodiment, the present invention comprises a topical doseform. “Topical administration” includes, for example, transdermaladministration, such as via transdermal patches or iontophoresisdevices, intraocular administration, or intranasal or inhalationadministration. Compositions for topical administration also include,for example, topical gels, sprays, ointments, and creams. A topicalformulation may include a compound which enhances absorption orpenetration of the active ingredient through the skin or other affectedareas. When the compounds of this invention are administered by atransdermal device, administration will be accomplished using a patcheither of the reservoir and porous membrane type or of a solid matrixvariety. Typical formulations for this purpose include gels, hydrogels,lotions, solutions, creams, ointments, dusting powders, dressings,foams, films, skin patches, wafers, implants, sponges, fibres, bandagesand microemulsions. Liposomes may also be used. Typical carriers includealcohol, water, mineral oil, liquid petrolatum, white petrolatum,glycerin, polyethylene glycol and propylene glycol. Penetrationenhancers may be incorporated—see, for example, B. C. Finnin and T. M.Morgan, J. Pharm. Sci., vol. 88, pp. 955-958, 1999.

Formulations suitable for topical administration to the eye include, forexample, eye drops wherein the compound of this invention is dissolvedor suspended in a suitable carrier. A typical formulation suitable forocular or aural administration may be in the form of drops of amicronized suspension or solution in isotonic, pH-adjusted, sterilesaline. Other formulations suitable for ocular and aural administrationinclude ointments, biodegradable (i.e., absorbable gel sponges,collagen) and non-biodegradable (i.e., silicone) implants, wafers,lenses and particulate or vesicular systems, such as niosomes orliposomes. A polymer such as crossed-linked polyacrylic acid, polyvinylalcohol, hyaluronic acid, a cellulosic polymer, for example,hydroxypropylmethylcellulose, hydroxyethylcellulose, or methylcellulose,or a heteropolysaccharide polymer, for example, gelan gum, may beincorporated together with a preservative, such as benzalkoniumchloride. Such formulations may also be delivered by iontophoresis.

For intranasal administration or administration by inhalation, theactive compounds of the invention are conveniently delivered in the formof a solution or suspension from a pump spray container that is squeezedor pumped by the patient or as an aerosol spray presentation from apressurized container or a nebulizer, with the use of a suitablepropellant. Formulations suitable for intranasal administration aretypically administered in the form of a dry powder (either alone, as amixture, for example, in a dry blend with lactose, or as a mixedcomponent particle, for example, mixed with phospholipids, such asphosphatidylcholine) from a dry powder inhaler or as an aerosol sprayfrom a pressurized container, pump, spray, atomizer (preferably anatomizer using electrohydrodynamics to produce a fine mist), ornebulizer, with or without the use of a suitable propellant, such as1,1,1,2-tetrafluoroethane or 1,1,1,2,3,3,3-heptafluoropropane. Forintranasal use, the powder may comprise a bioadhesive agent, forexample, chitosan or cyclodextrin.

In another embodiment, the present invention comprises a rectal doseform. Such rectal dose form may be in the form of, for example, asuppository. Cocoa butter is a traditional suppository base, but variousalternatives may be used as appropriate.

Other carrier materials and modes of administration known in thepharmaceutical art may also be used. Pharmaceutical compositions of theinvention may be prepared by any of the well-known techniques ofpharmacy, such as effective formulation and administration procedures.The above considerations in regard to effective formulations andadministration procedures are well known in the art and are described instandard textbooks. Formulation of drugs is discussed in, for example,Hoover, John E., Remington's Pharmaceutical Sciences, Mack PublishingCo., Easton, Pa., 1975; Liberman et al., Eds., Pharmaceutical DosageForms, Marcel Decker, New York, N.Y., 1980; and Kibbe et al., Eds.,Handbook of Pharmaceutical Excipients (3rd Ed.), American PharmaceuticalAssociation, Washington, 1999.

Co-Administration

The compounds of the present invention can be used, alone or incombination with other therapeutic agents, in the treatment of variousconditions or disease states. The compound(s) of the present inventionand other therapeutic agent(s) may be may be administered simultaneously(either in the same dosage form or in separate dosage forms) orsequentially. An exemplary therapeutic agent may be, for example, ametabotropic glutamate receptor agonist.

The administration of two or more compounds “in combination” means thatthe two compounds are administered closely enough in time that thepresence of one alters the biological effects of the other. The two ormore compounds may be administered simultaneously, concurrently orsequentially. Additionally, simultaneous administration may be carriedout by mixing the compounds prior to administration or by administeringthe compounds at the same point in time but at different anatomic sitesor using different routes of administration.

The phrases “concurrent administration,” “co-administration,”“simultaneous administration,” and “administered simultaneously” meanthat the compounds are administered in combination.

In one embodiment, the compounds of this invention are administered asadjunctive therapy with known anti-psychotics such as Ziprasidone(Geodon), Clozapine, Molindone, Loxapine, Pimozide, Risperidone,Olanzapine, Remoxipride, Sertindole, Amisulpride, Quetiapine,Prochlorperazine, Fluphenazine, Trifluoroperazine, Thioridazine,Haloperidol, Chlorpromazine, Flupentixol and Pipotiazine.

In another embodiment, the compounds of the present invention may alsobe used in combination with CNS agents such as antidepressants (such assertraline), anti-Parkinsonian drugs (such as deprenyl, L-dopa, Requip,Mirapex, MAOB inhibitors such as selegiline and rasagiline, COMTinhibitors such as Tasmar, A-2 inhibitors, dopamine reuptake inhibitors,NMDA antagonists, nicotine agonists, dopamine agonists and inhibitors ofneuronal nitric oxide synthase), anti-Alzheimer's drugs such asdonepezil, tacrine, alpha2delta inhibitors, COX-2 inhibitors, gabapentenoids, propentofylline or metrifonate, and antipyschotics such asPDE10 inhibitors, 5HT2C agonists, alpha 7 nicotinic receptor agonists,CB1 antagonists and compounds having activity antagonizing dopamine D2receptors.

Kits

The present invention further comprises kits that are suitable for usein performing the methods of treatment described above. In oneembodiment, the kit contains a first dosage form comprising one or moreof the compounds of the present invention and a container for thedosage, in quantities sufficient to carry out the methods of the presentinvention.

In another embodiment, the kit of the present invention comprises one ormore compounds of the invention.

In another embodiment, the invention relates to the novel intermediatesuseful for preparing the compounds of the invention.

The compounds of Formula I may be prepared by the methods describedbelow, together with synthetic methods known in the art of organicchemistry, or modifications and transformations that are familiar tothose of ordinary skill in the art. The starting materials used hereinare commercially available or may be prepared by routine methods knownin the art [such as those methods disclosed in standard reference bookssuch as the Compendium of Organic Synthetic Methods, Vol. I-XII(published by Wiley-Interscience)]. Preferred methods include, but arenot limited to, those described below.

During any of the following synthetic sequences it may be necessaryand/or desirable to protect sensitive or reactive groups on any of themolecules concerned. This can be achieved by means of conventionalprotecting groups, such as those described in T. W. Greene, ProtectiveGroups in Organic Chemistry, John Wiley & Sons, 1981; T. W. Greene andP. G. M. Wuts, Protective Groups in Organic Chemistry, John Wiley &Sons, 1991; and T. W. Greene and P. G. M. Wuts, Protective Groups inOrganic Chemistry, John Wiley & Sons, 1999, which are herebyincorporated by reference.

Compounds of Formula I, or their pharmaceutically acceptable salts, canbe prepared according to the reaction Schemes discussed herein below.Unless otherwise indicated, the substituents in the Schemes are definedas above. Isolation and purification of the products is accomplished bystandard procedures, which are known to a chemist of ordinary skill.

It will be understood by one skilled in the art that the varioussymbols, superscripts and subscripts used in the schemes, methods andexamples are used for convenience of representation and/or to reflectthe order in which they are introduced in the schemes, and are notintended to necessarily correspond to the symbols, superscripts orsubscripts in the appended claims. The schemes are representative ofmethods useful in synthesizing the compounds of the present invention.They are not to constrain the scope of the invention in any way.

Scheme 1 refers to the preparation of compounds of Formula I, wherein R³is H. Referring to Scheme 1, the compound of Formula I can be preparedfrom the compound of Formula S1 through removal of the two optionallypresent protecting groups P¹ and P². P¹ and P² in this case refer togroups well known to those skilled in the art for hydroxyl and amineprotection. For example, P¹ may be a benzyl group (Bn), which can becleaved via hydrogenation over a catalyst such as palladium, or throughtreatment with boron tribromide. P² may advantageously be atert-butoxycarbonyl group (Boc), which is normally removed throughtreatment with either HCl or trifluoroacetic acid, or abenzyloxycarbonyl group (CBZ), which may be cleaved using hydrogenationover a catalyst such as palladium.

Scheme 2 refers to the preparation of compounds S1 wherein P¹ is H andP² is Boc. Carboxylic acid S2 is converted to 2,2,2-trifluoroethyl esterS3 using 2,2,2-trifluoroethanol and a coupling reagent such as DCC,EDCl, or HBTU. 2,2,2-Trifluoroethyl ester S3 can also be synthesizedfrom S2 using 2,2,2-trifluoroethyl trifluoromethanesulfonate in thepresence of a base such as triethylamine, in a modification of theprocedures described by T. Kubota et al., J. Org. Chem. 1980, 45,5052-5057; and F. J. Lopez et al., Bioorg. Med. Chem. Lett. 2003, 13,1873-1878. Cyclic hydroxamic acid S1 is generated by reductivecyclization of S3 performed under hydrogenation conditions usingcatalysts such as Pt/C or Pt(S), through an adaptation of the work of T.J. McCord et al., J. Heterocycl. Chem. 1972, 9, 119. A commonly observedside reaction is over-reduction to the aniline, which generates a lactamside product; this can be removed by column chromatography. S1 can beconverted into a compound of Formula I according to the methods ofScheme 1.

Scheme 3 refers to the preparation of compound S7 (one enantiomer of S2wherein each R⁴ is H). Bromomethyl heteroaryl compound S4 can be reactedstereoselectively with tert-butyl N-(diphenylmethylene)glycinate, usinga chiral catalyst under basic conditions, such as cesium hydroxide, toprovide the protected amino acid derivative S5. This enantioselectiveroute is based on the work of S. Kumar and U. Ramachandran, Tetrahedron:Asymmetry 2003, 14, 2539-2545; and E. J. Corey et al., J. Am. Chem. Soc.1997, 119, 12414-12415. Amino acid deprotection is carried out underacidic conditions, for instance using aqueous HCl, to give the freeamino acid S6. Introduction of a Boc group onto the amine yields acidS7, which can be converted into a compound of Formula I according to themethods of Schemes 2 and 1. One skilled in the art will understand thatfor all of the stereoselective chemistry herein described, similarmethods may be used to prepare the opposite enantiomer of the compoundsshown, or the racemate thereof.

Incorporation of an R⁴ substituent can be achieved as described inScheme 4. Primary alcohol S8 can be oxidized to the correspondingaldehyde under Swern or Dess-Martin conditions; addition of a Grignardreagent (R⁴Mg-halide) then affords S9, which can be converted to thealkyl bromide S10 using standard conditions, such as subjection tophosphorus tribromide or carbon tetrabromide/triphenylphosphine.Diasteroselective phase-transfer-catalyzed alkylation of S10 with aglycinate Schiff base (see T. Ooi et al., Org. Lett. 2007, 9, 3945-3948)then affords S11. S11 may be converted into a compound of Formula Iaccording to the methods of Schemes 3, 2 and 1.

Alternatively, a Strecker synthesis can be employed, as depicted inScheme 5. Bromomethyl heteroaryl S4 is converted to the correspondingnitrile through reaction with cyanide ion, then alkylated under basicconditions with R⁴—Br to provide S13. Conversion of the nitrile of S13to aldehyde S14 is effected under standard conditions, for examplethrough reaction with diisobutylaluminum hydride. Asymmetric Streckersynthesis of S14 (see M. Shibasaki et al., Org. Reactions 2008, 70,1-119) then affords the amino nitrile S15, which is transformed to acompound of formula S2 by introduction of a Boc group and hydrolysis ofthe nitrile to the carboxylic acid. One skilled in the art willrecognize that this approach can also be used to introduce afluoromethyl group for R⁴ by reaction of the anion of S12 withformaldehyde, followed by conversion of the resulting alcohol to afluoro group via conversion to a leaving group such as tosylate,followed by displacement with fluoride ion. Compound S2 may be convertedinto a compound of Formula I according to the methods of Schemes 2 and1.

Scheme 6 refers to the preparation of bromomethyl nitro heteroaryl S4.o-Nitro-ester heteroaromatic compound S16 in which at least one R¹ is Hundergoes N-alkylation or N-arylation to give derivatives S17 wherein R¹is alkyl or aryl (see Scheme 7 for the more specific case wherein theheteroaryl group is a pyrazole; R″ in Scheme 7 is methyl or ethyl).Introduction of an alkyl group may be carried out with various alkyl orsubstituted alkyl bromide derivatives under standard basic conditions.Arylation can be carried out using Chan-Lam copper-mediated couplingwith arylboronic or heteroarylboronic acids, as described in Tetrahedron2009, 65, 3529-3535 and WO 2007/055941. In both cases the assignment ofthe regioisomers obtained (for instance, S19, S20, S22, and S23 inScheme 7) may be carried out using advanced NMR experiments such as NOEand HMBC. It will be noted by one skilled in the art that suchN-alkylation and N-arylation reactions may also be carried out on otherintermediates, such as but not limited to S29, S30 or S32; in such casesit may be advantageous to temporarily protect the heteroaryl nitrogen inquestion as, for example, its tert-butoxycarbonyl derivative, whilecarrying out earlier steps in the synthesis. If selective removal ofthis Boc group is required, in the case where more than one Boc ispresent, the basic method of S. E. Kazzouli et al., Tetrahedron Lett.2006, 47, 8575-8577 may be employed.

The resulting intermediate S17 can then be reduced using standardconditions such as lithium aluminum hydride, lithium borohydride orsodium borohydride in methanol, giving the corresponding alcohol S8, asshown in Scheme 6. Alternatively, the ester S17 can be hydrolyzed to thecorresponding carboxylic acid and reduced to the alcohol S8 using boranein tetrahydrofuran. Alcohol S8 is converted to bromide S4 according tostandard procedures, for example with phosphorus tribromide, asdescribed by R. M. Rzasa et al., Bioorg. Med. Chem. 2007, 15, 6574-6595,or by using carbon tetrabromide and triphenylphosphine. Bromide S4 canbe converted into a compound of Formula I using the methods of Schemes5, 3, 2 and 1, while alcohol S8 may be converted to Formula I accordingto Schemes 4, 2 and 1.

Scheme 8 depicts several methods of preparation for key esterintermediate S16. Nitration of 5-membered heteroaryl compound S24affords nitro compound S25. Oxidation of the methyl group, as describedin WO 2006/046135 and U.S. Pat. No. 4,282,361, gives the correspondingcarboxylic acid S26, which may be converted to ester S16 via Fischeresterification. When carboxylic acid S27 is available, compound S26 maybe directly obtained by nitration. In cases where the requiredaminoheteroaryl ester S28 is commercially available or known in theliterature, it can be oxidized to afford nitro heteroaryl S16 withsodium perborate in glacial acetic acid or in trifluoroacetic acid,using a modified version of the procedure described in US 2006/0009509.The oxidation reaction can also be performed withZr(Ot-Bu)₄/tert-butylhydroperoxide, in a modification of the proceduresdescribed in Eur. J. Org. Chem. 1998, 679-682; J. Prakt. Chem. 1997,339, 335-339; and Advanced Synthesis and Catalysis 2009, 351, 93-96.Ester S16 can be converted into a compound of Formula I using themethods of Schemes 6, 3, 2 and 1.

An alternate approach to heteroaryl acid S7 is shown in Scheme 9. Bromonitro heteroaryl compound S29 (generally available either viabromination of the corresponding nitro heteroaryl using bromine orN-bromosuccinimide, or via bromination of a heteroaryl followed bynitration; alternatively, a Hunsdiecker reaction can be carried out onthe corresponding carboxylic acid derived from hydrolysis of S16 or S17)can be subjected to a Negishi coupling with an appropriately protectediodoalanine derivative to provide S30 (see R. F. W. Jackson et al., J.Org. Chem. 2010, 75, 245-248). Subsequent ester hydrolysis, for exampleunder standard saponification conditions, affords acid S7. In thespecific case of a pyrazole, nitropyrazoles are available via the nitrorearrangement chemistry described by J. W. A. M. Janssen et al., J. Org.Chem. 1973, 38, 1777-1782. S7 can be converted into a compound ofFormula I according to the methods of Schemes 2 and 1.

In certain cases, as shown in Scheme 10, a palladium-catalyzed Suzukireaction is a suitable alternative to the Negishi reaction forinstalling the amino acid, through reaction of bromo compound S29 with aboronate such as[(2S)-2-[(tert-butoxycarbonyl)amino]-3-{[2-(trimethylsilyl)ethoxy]methoxy}propyl]boronicacid (S31) (C. W. Barfoot et al., Tetrahedron 2005, 61, 3403-3417). Theresulting derivative S32 can be deprotected via removal of the SEMprotecting group, then oxidized to carboxylic acid S7 using the generalchemistry described by Barfoot et al. S7 may be converted into acompound of Formula I according to the methods of Schemes 2 and 1.

Scheme 11 refers to the preparation of substituted pyrazoles of thegeneral formula S29 (e.g., S34). A 4-bromopyrazole S33 can undergostep-wise nitration and N-alkylation (see J. Chem. Soc., Perkin Trans I1984, 63-67) to provide 4-bromo-5-nitropyrazole S34. Alternatively, a5-amino-4-bromopyrazole S36 can be subjected to oxidation as outlined inScheme 8, to provide S34. Alternatively, Hunsdiecker reaction of4-carboxy-pyrazole S35 affords 4-bromo-5-nitropyrazole S34. Pyrazole S34can be converted into S37, which represents a subset of the compounds ofFormula I, using the methods of Schemes 9 or 10, followed by Schemes 2and 1.

Nitro compounds of the general formula S29 can also be prepared throughoxidation of the corresponding amine S38 as shown in Scheme 12, usingchemistry described for conversion of S28 to S16 in Scheme 8. Analternative approach to amine oxidation involves initial derivatizationof the amino group of S38 as its benzaldehyde imine S39, followed bymeta-chloroperoxybenzoic acid oxidation to provide the oxaziridine S40.Acid-catalyzed isomerization to nitrone S41, as described by Y-M. Linand M. J. Miller, J. Org. Chem. 1999, 64, 7451-7458, is followed byNegishi cross-coupling to provide protected amino acid S42.Acid-mediated hydrolysis of the benzylidene group, as described by Linand Miller, and ester hydrolysis, followed by amide coupling of theliberated hydroxylamine to the carboxylic acid group, affords S43, whichrepresents a subset of the compounds of Formula I.

In cases where the nitro-substituted heteroaryl compound S29 isdifficult to obtain, an alternate bond formation can be used to generatethe compounds of Formula I, as depicted in Scheme 13. Negishi reactionof bromo heteroaryl compound S44 to provide protected amino acid S45wherein R″ is methyl or ethyl, as described in Scheme 9, is followed byhydrolysis to the carboxylic acid and conversion to amide S46 throughcoupling with an O-protected hydroxylamine derivative. The resultingamide, upon treatment with phenyliodine(III) bis(trifluoroacetate)(PIFA) then undergoes a nitrenium ion cyclization reaction to affordS47, using the method of A. Correa et al., Tetrahedron 2003, 59,7103-7110. One skilled in the art will recognize that where one of X, Yor Z in the heteroaryl ring of S47 is CH, installation of R² can beeffected at this stage through either palladium-mediated C—H activationchemistry (see I. V. Seregin and V. Gevorgyan, Chem. Soc. Rev. 2007, 36,1173-1193), or through bromination followed by a palladium-catalyzedcross-coupling reaction. Compound S47 may be converted into a compoundof Formula I according to Scheme 1.

Preparation of specific heteroaryl intermediates is described in thefollowing schemes.

The pyrazole ring may be synthesized as depicted in Scheme 14.Condensation of ethyl cyanoacetate or malononitrile with an alkyl oraryl acid chloride gives enol intermediate S48. S48 can be converted tothe corresponding vinyl chloride or alkyl vinyl ether S49 under standardconditions (e.g., treatment with phosphorus oxychloride or reaction withmethyl or ethyl iodide in the presence of silver carbonate); in cases inwhich the vinyl chloride is particularly unstable, the alkyl vinyl ethermay provide a more stable alternative. Intermediate S49 can beselectively converted to pyrazole S50 via condensation with theappropriate hydrazine. The regioisomer S51 can be obtained viacondensation of S49 with the preformed hydrazone derived frombenzaldehyde, as described by Y. Xia et al., J. Med. Chem. 1997, 40,4372-4377. Oxidation of either S50 or S51 to the corresponding nitrocompound can be effected as described in Scheme 8; the nitro compoundcan then be converted into a compound of Formula I using the methods ofSchemes 6, 3, 2 and 1.

The synthesis of intermediates S55 and S57 is shown in Scheme 15.Compound S52, which may be prepared as reported by M. Kim et al., Arch.Pharmacal. Res. 2004, 27, 151-155, is converted to thioamide S53 viatreatment with Lawesson's reagent, as described by W. Luo et al.,Synthesis 2008, 3415-3422. Conversion of S53 to enamine S54 is thencarried out with N,N-dimethylformamide and phosphorus oxychloride, usingthe method of J. Liebscher and B. Abegaz, Synthesis 1982, 769-771.Cyclization to the pyrazole S55 is carried out by reaction with asubstituted hydrazine. Alternatively, compound S52 can be brominated atthe alpha position to afford S56 and then transformed into thecorresponding imidazole

S57 through reaction with an optionally substituted amidine, using thegeneral method described by F. Denorme et al., PCT Int Appl. WO2008012010 A1. Compounds S55 and S57 can be converted to compounds ofFormula I according to the methods of Scheme 1.

As shown in Scheme 16, compounds of Formula I wherein R³ is H can beconverted to carbamate prodrugs of Formula I wherein R³ isC(═O)NR^(7a)R^(7b) by reaction with the appropriate carbamoyl chloridein the presence of a base such as pyridine. It may be advantageous totemporarily protect the free primary amino group prior to thistransformation. Similarly, use of an acyl chloride [ClC(═O)R⁷] or acylanhydride {[R⁷C(═O)]₂O} provides the corresponding ester prodrug[Formula I wherein R³ is C(═O)R⁷], while a chloroformate reactant[ClC(═O)OR⁷] can be used to prepare the carbonate prodrug [Formula Iwherein R³ is C(═O)OR⁷]. Prodrugs of formula S59 (which are alsocompounds of Formula I), wherein R⁹ is as defined above, can be preparedvia alkylation of the compound of Formula I wherein R³ is H withcompound S58 (LV═CH₃SO₃, Cl, Br) in the presence of a base such aspotassium carbonate.

Experiments were generally carried out under inert atmosphere (nitrogenor argon), particularly in cases where oxygen- or moisture-sensitivereagents or intermediates were employed. Commercial solvents andreagents were generally used without further purification, includinganhydrous solvents where appropriate (generally Sure-Seal™ products fromthe Aldrich Chemical Company, Milwaukee, Wis.). Products were generallydried under vacuum before being carried on to further reactions orsubmitted for biological testing. Mass spectrometry data is reportedfrom either liquid chromatography-mass spectrometry (LCMS), atmosphericpressure chemical ionization (APCI) or gas chromatography-massspectrometry (GCMS) instrumentation. Chemical shifts for nuclearmagnetic resonance (NMR) data are expressed in parts per million (ppm,δ) referenced to residual peaks from the deuterated solvents employed.

For syntheses referencing procedures in other Examples or Methods,reaction conditions (length of reaction and temperature) may vary. Ingeneral, reactions were followed by thin layer chromatography or massspectrometry, and subjected to work-up when appropriate. Purificationsmay vary between experiments: in general, solvents and the solventratios used for eluants/gradients were chosen to provide appropriateR_(f)s or retention times.

EXAMPLES Example 1(5S)-5-Amino-2-benzyl-7-hydroxy-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one,HCl salt (1)

Step 1. Synthesis of ethyl 5-nitro-1H-pyrazole-4-carboxylate (C1)

A mixture of sodium perborate tetrahydrate (95%, 15.7 g, 96.9 mmol) andacetic acid (60 mL) was heated to 85° C. Ethyl5-amino-1H-pyrazole-4-carboxylate (3.0 g, 19 mmol) was added, and themixture was allowed to react at 85° C. for 18 hours. The reaction wasthen poured into water and extracted with EtOAc. The combined organiclayers were dried over magnesium sulfate, filtered and concentrated invacuo; purification via silica gel chromatography (Gradient: 0% to 100%EtOAc in heptane) provided C1. Yield: 1.41 g, 7.62 mmol, 40%. LCMS m/z184.0 (M−1). ¹H NMR (400 MHz, CDCl₃) δ 1.39 (t, J=7.2 Hz, 3H), 4.40 (q,J=7.1 Hz, 2H), 8.32 (s, 1H).

Step 2. Synthesis of ethyl 1-benzyl-3-nitro-1H-pyrazole-4-carboxylate(C2)

To a solution of C1 (2.86 g, 15.4 mmol) in N,N-dimethylformamide (60 mL)was added anhydrous potassium carbonate (12.8 g, 92.6 mmol), benzylbromide (2.20 mL, 18.5 mmol) and a catalytic amount of potassium iodide.The reaction was heated at 60° C. for 18 hours, then diluted with EtOAcand washed with water. The organic layer was dried over magnesiumsulfate, filtered and concentrated under reduced pressure. Purificationusing silica gel chromatography (Gradient: 0% to 100% EtOAc in heptane)provided C2 as an oil. Yield: 1.35 g, 4.90 mmol, 32%. An NOE experimentrevealed a strong interaction between the pyrazole CH and aromaticprotons on the phenyl group, supporting the indicated regiochemistry forC2. LCMS m/z 276.0 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 1.32 (t, J=7.1 Hz,3H), 4.31 (q, J=7.1 Hz, 2H), 5.33 (s, 2H), 7.30-7.35 (m, 2H), 7.40-7.45(m, 3H), 7.78 (s, 1H).

Step 3. Synthesis of (1-benzyl-3-nitro-1H-pyrazol-4-yl)methanol (C3)

A solution of C2 (1.35 g, 4.90 mmol) in tetrahydrofuran (40 mL) wascooled to −40° C. and treated with lithium aluminum hydride (99%, 1 M,10.3 mL, 10.3 mmol). The reaction was allowed to stir for 20 minutes at−40° C., then was quenched with saturated aqueous ammonium chloridesolution. After addition of EtOAc and water, the layers were separatedand the aqueous layer was extracted with EtOAc. The combined organiclayers were dried over magnesium sulfate, filtered, and concentrated invacuo to provide C3 as a solid. Yield: 1.29 g, 5.53 mmol, quantitative.¹H NMR (500 MHz, CDCl₃) δ 2.63 (br t, J=6 Hz, 1H), 4.79 (br d, J=5.4 Hz,2H), 5.33 (s, 2H), 7.29-7.32 (m, 2H), 7.36-7.41 (m, 3H), 7.42 (s, 1H).

Step 4. Synthesis of 1-benzyl-4-(bromomethyl)-3-nitro-1H-pyrazole (C4)

Carbon tetrabromide (3.67 g, 11.1 mmol) and triphenylphosphine (2.43 mL,11.1 mmol) were added to a solution of C3 (1.29 g, 5.53 mmol) indichloromethane (150 mL), and the reaction was allowed to stir at RT for18 hours. After being washed with water, the reaction mixture was driedover magnesium sulfate, filtered, and concentrated under reducedpressure. Silica gel chromatography (Gradient: 0% to 100% EtOAc inheptane) afforded C4 as a solid. Yield: 951 mg, 3.21 mmol, 58%. LCMS m/z297.9 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 4.60 (d, J=0.6 Hz, 2H), 5.32 (s,2H), 7.28-7.32 (m, 2H), 7.36-7.41 (m, 3H), 7.52 (br s, 1H).

Step 5. Synthesis of tert-butyl3-(1-benzyl-3-nitro-1H-pyrazol-4-yl)-N-(diphenylmethylene)-L-alaninate(C5)

To a −30° C. solution of tert-butyl N-(diphenylmethylene)glycinate (98%1.16 g, 3.85 mmol), C4 (951 mg, 3.21 mmol) andO-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (95%, 0.205 g,0.322 mmol) in dichloromethane (25 mL) was added cesium hydroxidemonohydrate (0.647 g, 3.85 mmol). (See E. J. Corey et al., J. Am. Chem.Soc. 1997, 119, 12414-12415.) The reaction was stirred at −30° C. for 18hours, then washed with water, dried over magnesium sulfate, filteredand concentrated under reduced pressure. The residue was purified bychromatography on silica gel (Eluants: dichloromethane, then EtOAc) togive C5 as a gum. Yield: 1.63 g, 3.19 mmol, 99%. LCMS m/z 511.3 (M+1).¹H NMR (400 MHz, CDCl₃) δ 1.39 (s, 9H), 3.24 (dd, half of ABX pattern,J=14.3, 8.2 Hz, 1H), 3.38 (br dd, half of ABX pattern, J=14.3, 4.6 Hz,1H), 4.22 (dd, J=8.3, 4.6 Hz, 1H), 5.25 (AB quartet, J_(AB)=14.6 Hz,Δν_(AB)=18.3 Hz, 2H), 6.72 (br d, J=7 Hz, 2H), 7.16-7.22 (m, 4H),7.25-7.44 (m, 8H), 7.50-7.54 (m, 2H).

Step 6. Synthesis of 3-(1-benzyl-3-nitro-1H-pyrazol-4-yl)-L-alanine, HClsalt (C6)

A solution of C5 (1.63 g, 3.19 mmol) in dichloromethane (100 mL) wastreated with trifluoroacetic acid (15 mL) and allowed to stir for 66hours. The reaction mixture was concentrated, and the residue waspartitioned between diethyl ether and aqueous 4 N HCl. The organic layerwas extracted with aqueous 4 N HCl, and the combined aqueous layers wereconcentrated in vacuo (azeotroping with methanol) to provide C6 as ayellow gum (1.05 g), which was used directly in the next step. LCMS m/z291.0 (M+1).

Step 7. Synthesis of3-(1-benzyl-3-nitro-1H-pyrazol-4-yl)-N-(tert-butoxycarbonyl)-L-alanine(C7)

A solution of C6 (≦3.19 mmol) in tetrahydrofuran (12.9 mL) was treatedwith aqueous sodium hydroxide solution (1 M, 12.9 mL, 12.9 mmol)followed by di-tert-butyl dicarbonate (0.842 g, 3.86 mmol). The reactionwas allowed to stir at RT for 18 hours, and then was neutralized by theaddition of aqueous ammonium chloride solution and aqueous HCl. Themixture was extracted with EtOAc, and the combined organic extracts weredried over magnesium sulfate, filtered and concentrated under reducedpressure to provide C7 as a solid, contaminated with benzophenone.Corrected yield: 830 mg, 2.13 mmol, 67% from step 6. LCMS m/z 389.1(M−1). ¹H NMR (400 MHz, CD₃OD) δ 1.33 (s, 9H), 3.01 (dd, J=14.7, 9.5 Hz,1H), 3.41 (dd, J=14.6, 4.6 Hz, 1H), 4.35 (dd, J=9.6, 4.7 Hz, 1H), 5.35(s, 2H), 7.30-7.39 (m, 5H), 7.69 (s, 1H).

Step 8. Synthesis of 2,2,2-trifluoroethyl3-(1-benzyl-3-nitro-1H-pyrazol-4-yl)-N-(tert-butoxycarbonyl)-L-alaninate(C8)

1-[3-(Dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (98%, 361mg, 1.85 mmol), 4-(dimethylamino)pyridine (97%, 116 mg, 0.921 mmol) and2,2,2-trifluoroethanol (99%, 1.36 mL, 18.5 mmol) were added to asolution of C7 (0.36 g, 0.92 mmol) in dichloromethane (30 mL), and thereaction mixture was allowed to stir for 18 hours. The reaction waswashed with water, dried over magnesium sulfate, filtered andconcentrated in vacuo. Purification via silica gel chromatography(Gradient: 0% to 100% EtOAc in heptane) afforded C8 as a solid. Yield:223 mg, 0.472 mmol, 51%. LCMS m/z 471.1 (M−1). ¹H NMR (400 MHz, CDCl₃) δ1.37 (s, 9H), 3.24 (br dd, half of ABX pattern, J=14.7, 7.9 Hz, 1H),3.35 (dd, half of ABX system, J=15.0, 5.7 Hz, 1H), 4.42-4.52 (m, 2H),4.59 (br ddd, J=8, 8, 6 Hz, 1H), 5.13 (br d, J=8 Hz, 1H), 5.31 (s, 2H),7.26-7.32 (m, 3H), 7.36-7.42 (m, 3H).

Step 9. Synthesis of tert-butyl[(5S)-2-benzyl-7-hydroxy-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridin-5-yl]carbamate(C9)

To a solution of C8 (110 mg, 0.233 mmol) in pyridine (10 mL) was added5% platinum on carbon (35 mg, 0.0090 mmol), and the reaction wassubjected to hydrogenation at 30 psi for 3 hours on a Parr shaker. Afterfiltration through Celite, the filter pad was rinsed with EtOAc (10 mL)and the combined filtrates were concentrated in vacuo. Purificationusing silica gel chromatography (Gradient: 0% to 100% EtOAc in heptane)provided C9 as a solid. Yield: 55 mg, 0.15 mmol, 64%. LCMS m/z 359.2(M+1). ¹H NMR (400 MHz, CDCl₃) δ 1.48 (s, 9H), 2.49 (br dd, J=14, 14 Hz,1H), 3.30 (br dd, J=14, 7 Hz, 1H), 4.20-4.29 (m, 1H), 5.21 (AB quartet,J_(AB)=15.2 Hz, Δν_(AB)=11.1 Hz, 2H), 5.61 (br s, 1H), 7.07-7.08 (m,1H), 7.14-7.20 (m, 2H), 7.29-7.36 (m, 3H), 10.74 (br s, 1H).

Step 10. Synthesis of Example 1

C9 (29 mg, 0.081 mmol) was dissolved in a minimum quantity ofdichloromethane (approximately 0.3 mL) and treated with a solution ofHCl (4 N in 1,4-dioxane, 1 mL, 4 mmol). After 1 hour at RT, the reactionwas concentrated in vacuo to provide a solid, which was slurried indiethyl ether and filtered to afford a white solid for Example 1. Yield:13 mg, 0.044 mmol, 54%. LCMS m/z 259.2 (M+1). ¹H NMR (400 MHz, CD₃OD) δ2.85 (ddd, J=14.6, 13.7, 1.0 Hz, 1H), 3.24 (dd, J=14.6, 7.4 Hz, 1H),4.39 (dd, J=13.7, 7.4 Hz, 1H), 5.24 (s, 2H), 7.26-7.36 (m, 5H), 7.57 (d,J=0.8 Hz, 1H).

Example 2(5S)-5-Amino-3-benzyl-7-hydroxy-1-methyl-1,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one,trifluoroacetate salt (2)

Step 1. Synthesis of5-amino-3-benzyl-1-methyl-1H-pyrazole-4-carbonitrile (C10)

A mixture of (1-methoxy-2-phenylethylidene)malononitrile (prepared bythe method of B. C. Kraybill et al., J. Am. Chem. Soc. 2002, 124,12118-12128; 10 g, 50 mmol) and methylhydrazine (2.3 g, 50 mmol) inethanol (120 mL) was heated to reflux for 10 minutes. The reaction wasconcentrated in vacuo, and the residue was diluted with water (200 mL)and extracted with EtOAc (3×100 mL). The combined organic layers werewashed with brine, dried over sodium sulfate, filtered and concentratedunder reduced pressure to afford C10 as a yellow solid. Yield: 10 g, 47mmol, 94%.

Step 2. Synthesis of 5-amino-3-benzyl-1-methyl-1H-pyrazole-4-carboxylicacid (C11)

To a solution of sodium hydroxide (10 g, 0.25 mol) in water (100 mL) wasadded C10 (5.00 g, 23.6 mmol) in one portion. The mixture was heated atreflux for 18 hours, then cooled to RT and extracted with EtOAc (3×100mL). The aqueous layer was neutralized to a pH of 6 to 7 using aqueous 1N HCl, and then extracted with EtOAc (3×150 mL). The combined organiclayers from the neutral extraction were washed with brine, dried oversodium sulfate, filtered and concentrated in vacuo. Purification viasilica gel chromatography (Eluant: 1:1 EtOAc/petroleum ether) affordedC11 as a white solid. Yield: 4.7 g, 20 mmol, 85%. ¹H NMR (400 MHz,DMSO-d₆) δ 3.47 (s, 3H), 3.94 (s, 2H), 6.15 (br s, 2H), 7.10-7.26 (m,5H), 11.80 (br s, 1H).

Step 3. Synthesis of 3-benzyl-1-methyl-5-nitro-1H-pyrazole-4-carboxylicacid (C12)

A solution of sodium nitrite (3.00 g, 43.5 mmol) in water (2 mL) wasadded slowly, in a drop-wise fashion, to a 0° C. suspension of C11 (5.00g, 21.6 mmol) in aqueous tetrafluoroboric acid (48%, 500 mL). Thereaction was maintained at −5 to 0° C. for five minutes, then added over30 minutes to a suspension of copper (5.0 g, 79 mmol) in saturatedaqueous sodium nitrite solution, while keeping the internal temperaturebelow 0° C. The reaction was stirred at −5 to 0° C. for one hour, andthe resulting mixture was extracted with EtOAc (3×200 mL). The combinedorganic layers were washed with brine, dried over sodium sulfate,filtered and concentrated in vacuo. Silica gel chromatography (Eluant:1:1 EtOAc/petroleum ether) provided C12 as a pale yellow solid. Yield:3.5 g, 13 mmol, 60%. ¹H NMR (400 MHz, CD₃OD) δ 3.98 (s, 3H), 4.14 (s,2H), 7.12-7.26 (m, 5H).

Step 4. Synthesis of (3-benzyl-1-methyl-5-nitro-1H-pyrazol-4-yl)methanol(C13)

Borane-methyl sulfide complex (2 M in tetrahydrofuran, 18 mL, 36 mmol)was added drop-wise to a −20° C. solution of C12 (4.7 g, 18 mmol) intetrahydrofuran (120 mL), and the reaction mixture was then heated toreflux for 2 hours. The resulting mixture was cooled, poured into water(100 mL), and concentrated under reduced pressure. The remaining aqueousmaterial was extracted with EtOAc (3×100 mL), and the combined organiclayers were washed with brine, dried over sodium sulfate, filtered andconcentrated in vacuo to afford C13 as a white solid. Yield: 3.5 g, 14mmol, 78%. LCMS m/z 248.1 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 2.34 (t,J=7.0 Hz, 1H), 4.09 (s, 2H), 4.23 (s, 3H), 4.68 (d, J=7.0 Hz, 2H),7.23-7.36 (m, 5H).

Step 5. Synthesis of3-benzyl-4-(bromomethyl)-1-methyl-5-nitro-1H-pyrazole (C14)

C13 was converted to C14 according to the general procedure for thesynthesis of C4 in Example 1. C14 was obtained as an oil. Yield: 969 mg,3.12 mmol, 71%. LCMS m/z 311.9 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 4.06 (brs, 2H), 4.22 (s, 3H), 4.50 (s, 2H), 7.23-7.35 (m, 5H).

Step 6. Synthesis of tert-butyl3-(3-benzyl-1-methyl-5-nitro-1H-pyrazol-4-yl)-N-(diphenylmethylene)-L-alaninate(C15)

C14 was converted to C15 according to the general procedure for thesynthesis of C5 in Example 1. C15 was obtained as an oil. Yield: 771 mg,1.47 mmol, 47%. LCMS m/z 525.1 (M+1). ¹H NMR (500 MHz, CDCl₃) δ 1.47 (s,9H), 3.20 (dd, half of ABX pattern, J=13.8, 9.9 Hz, 1H), 3.32 (dd, halfof ABX pattern, J=13.9, 3.7 Hz, 1H), 3.84 (d, J=15.6 Hz, 1H), 4.04 (d,J=15.6 Hz, 1H), 4.13 (s, 3H), 4.28 (dd, J=9.9, 3.7 Hz, 1H), 6.71 (br d,J=7 Hz, 2H), 7.15-7.21 (m, 3H), 7.22-7.27 (m, 2H), 7.31-7.42 (m, 6H),7.62-7.65 (m, 2H).

Step 7. Synthesis of3-(3-benzyl-1-methyl-5-nitro-1H-pyrazol-4-yl)-L-alanine, HCl salt (C16)

C15 (505 mg, 0.963 mmol) was dissolved in acetonitrile (10 mL) andtreated with concentrated aqueous HCl (3 mL). The reaction was heated atreflux for 20 hours, then cooled to RT and filtered. The filtrate wasconcentrated in vacuo, and the residue was partitioned between diethylether and 1 N aqueous HCl. The aqueous layer was washed once withdiethyl ether and then concentrated under reduced pressure, azeotropingwith toluene, to provide crude C16, which was taken directly to the nextstep without further purification. LCMS m/z 305.1 (M+1). ¹H NMR (400MHz, CD₃OD) δ 3.20 (dd, half of ABX pattern, J=14.4, 7.5 Hz, 1H), 3.34(dd, half of ABX pattern, J=14.5, 7.5 Hz, 1H, assumed; partiallyobscured by solvent peak), 3.80 (dd, J=7.6, 7.5 Hz, 1H), 4.03 (ABquartet, J_(AB)=15.8 Hz, Δν_(AB)=15.9 Hz, 2H), 4.20 (s, 3H), 7.19-7.31(m, 5H).

Step 8. Synthesis of3-(3-benzyl-1-methyl-5-nitro-1H-pyrazol-4-yl)-N-(tert-butoxycarbonyl)-L-alanine(C17)

C16 (≦0.963 mmol) was suspended in a mixture of water (10 mL) and1,4-dioxane (10 mL). Triethylamine (97%, 0.464 mL, 3.23 mmol) was added,followed by di-tert-butyl dicarbonate (98%, 360 mg, 1.62 mmol), and thereaction was allowed to stir for 18 hours. Additional triethylamine (2equivalents) and di-tert-butyl dicarbonate (0.5 equivalents) were addedto the reaction, and stirring was continued for an additional 2 hours.The reaction was partitioned between EtOAc and aqueous citric acidsolution. The aqueous layer (pH ˜5) was extracted twice with EtOAc, andthe combined organic layers were dried over magnesium sulfate, filteredand concentrated in vacuo to provide C17 as an oil. Yield: 266 mg, 0.658mmol, 68% from step 7. LCMS m/z 405.2 (M+1). ¹H NMR (400 MHz, CDCl₃) δ1.37 (br s, 9H), 3.02 (dd, J=14, 9 Hz, 1H), 3.26 (br dd, J=14, 5 Hz,1H), 4.02 (AB quartet, 2 downfield peaks are broad, J_(AB)=15.6 Hz,Δν_(AB)=26.4 Hz, 2H), 4.17 (s, 3H), 4.42-4.51 (br m, 1H), 5.00 (br d,J=8 Hz, 1H), 7.19-7.32 (m, 5H).

Step 9. Synthesis of 2,2,2-trifluoroethyl3-(3-benzyl-1-methyl-5-nitro-1H-pyrazol-4-yl)-N-(tert-butoxycarbonyl)-L-alaninate(C18)

2,2,2-Trifluoroethyl trifluoromethanesulfonate (198 mg, 0.853 mmol) wasadded to a solution of C17 (266 mg, 0.658 mmol) and triethylamine (0.229mL, 1.64 mmol) in tetrahydrofuran (5 mL), and the mixture was heated at60° C. for 19 hours, then allowed to stir at RT for 4 days. Afterremoval of volatiles in vacuo, the residue was partitioned betweendiethyl ether and water. The organic layer was washed with brine, thenconcentrated in vacuo. Purification using silica gel chromatography(Gradient: 0% to 40% EtOAc in heptane) provided C18 as a yellow oil.Yield: 218 mg, 0.448 mmol, 68%. LCMS m/z 387.2 [(M-CO₂ and2-methylprop-1-ene)+1]. ¹H NMR (400 MHz, CDCl₃) δ 1.39 (br s, 9H), 3.06(dd, half of ABX pattern, J=14.0, 8.8 Hz, 1H), 3.17 (br dd, half of ABXpattern, J=14, 6 Hz, 1H), 4.01 (AB quartet, 2 downfield peaks are broad,J_(AB)=15.6 Hz, Δν_(AB)=33 Hz, 2H), 4.19 (s, 3H), 4.41-4.58 (m, 3H),4.88 (br d, J=8 Hz, 1H), 7.21-7.33 (m, 5H).

Step 10. Synthesis of tert-butyl[(5S)-3-benzyl-7-hydroxy-1-methyl-6-oxo-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridin-5-yl]-carbamate(C19)

A mixture of C18 (215 mg, 0.442 mmol) and 5% platinum on carbon (172 mg)in pyridine (10 mL) was hydrogenated for 3 hours on a Parr shaker at 30psi hydrogen. The reaction was filtered through Celite, and the filterpad was washed with EtOAc (30 mL) and methanol (10 mL). The filtrate wasconcentrated in vacuo, and the residue was triturated with diethyl etherto provide 55 mg of a white solid. Purification using silica gelchromatography (Gradients: 0% to 100% EtOAc in heptane, then 0% to 15%methanol in EtOAc, then eluted with 15% methanol in dichloromethane)provided C19 as a white solid. Yield: 50 mg, 0.13 mmol, 29%. Additionalproduct could be obtained by purification of the filtrate from thetrituration described above. LCMS m/z 373.2 (M+1). ¹H NMR (400 MHz,CD₃OD) δ 1.45 (br s, 9H), 2.42 (dd, J=14.8. 13.7 Hz, 1H), 2.70 (dd,J=14.9, 7.1 Hz, 1H), 3.87 (s, 2H), 3.90 (s, 3H), 4.36-4.43 (m, 1H),7.15-7.29 (m, 5H).

Step 11. Synthesis of Example 2

Trifluoroacetic acid (1 mL) was added to a solution of C19 (21 mg, 0.056mmol) in dichloromethane (2 mL), and the reaction was allowed to stirfor 1 hour at RT. Removal of solvents in vacuo provided a beige solidfor Example 2. Yield: 20 mg, 0.052 mmol, 93%. ¹H NMR (400 MHz, CD₃OD) δ2.55 (dd, J=14, 14 Hz, 1H), 2.86 (dd, J=14.4, 7.4 Hz, 1H), 3.89-3.91 (m,2H), 3.93 (s, 3H), 4.34 (dd, J=13.7, 7.4 Hz, 1H), 7.17-7.31 (m, 5H).

Example 3(5S)-5-Amino-3-benzyl-7-hydroxy-2-methyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one,HCl salt (3)

Step 1. Synthesis of ethyl5-benzyl-1-methyl-3-nitro-1H-pyrazole-4-carboxylate (C20)

A mixture of sodium perborate tetrahydrate (95%, 3.12 g, 19.3 mmol) andtrifluoroacetic acid (10 mL) was heated to 75° C. To this was added asolution of ethyl 3-amino-5-benzyl-1-methyl-1H-pyrazole-4-carboxylate(prepared according to the method of Y. Xia et al., J. Med. Chem. 1997,40, 4372-4377; 1.00 g, 3.86 mmol) in trifluoroacetic acid, and themixture was allowed to react at 75° C. for 2.5 hours. The reaction wasthen cooled, poured into water and extracted with EtOAc. The combinedorganic layers were washed with water, dried over magnesium sulfate,filtered and concentrated in vacuo; purification via silica gelchromatography (Eluant: 30% EtOAc in heptane) provided C20 as a darkyellow oil. Yield: 333 mg, 1.15 mmol, 30%. LCMS m/z 290.2 (M+1). ¹H NMR(400 MHz, CDCl₃) δ 1.32 (t, J=7.1 Hz, 3H), 3.74 (s, 3H), 4.33 (br s,2H), 4.34 (q, J=7.1 Hz, 2H), 7.14-7.18 (m, 2H), 7.25-7.30 (m, 1H),7.31-7.36 (m, 2H).

Step 2. Synthesis of 5-benzyl-1-methyl-3-nitro-1H-pyrazole-4-carboxylicacid (C21)

Lithium hydroxide (1 M aqueous solution, 4.11 mL, 4.11 mmol) was addedto a solution of C20 (793 mg, 2.74 mmol) in tetrahydrofuran (8 mL) andmethanol (4 mL), and the reaction was allowed to stir for 20 hours.After removal of solvents in vacuo, the residue was acidified with 1 Naqueous HCl and extracted with EtOAc. The combined organic layers werewashed with water and with brine, then dried over magnesium sulfate,filtered and concentrated under reduced pressure, affording C21 as anoil. Yield: 656 mg, 2.51 mmol, 92%. LCMS m/z 260.1 (M−1). ¹H NMR (400MHz, CDCl₃) δ 3.79 (s, 3H), 4.47 (br s, 2H), 7.13-7.17 (m, 2H),7.25-7.30 (m, 1H), 7.31-7.36 (m, 2H).

Step 3. Synthesis of (5-benzyl-1-methyl-3-nitro-1H-pyrazol-4-yl)methanol(C22)

A solution of borane in tetrahydrofuran (1 M, 10.0 mL, 10.0 mmol) wasadded to a solution of C21 (656 mg, 2.51 mmol) in tetrahydrofuran (20mL), and the reaction was heated to 50° C. for 5 hours. The reaction wasslowly added to water (50 mL), acidified with 0.5 N HCl, and extractedwith EtOAc. The combined organic layers were washed with water, washedwith brine and dried over magnesium sulfate. After filtration, thefiltrate was concentrated in vacuo to afford C22 as a colorless oil.Yield: 583 mg, 2.36 mmol, 94%. ¹H NMR (400 MHz, CDCl₃) δ 3.76 (s, 3H),4.12 (s, 2H), 4.77 (br s, 2H), 7.09-7.13 (m, 2H), 7.25-7.30 (m, 1H),7.31-7.37 (m, 2H).

Step 4. Synthesis of5-benzyl-4-(bromomethyl)-1-methyl-3-nitro-1H-pyrazole (C23)

Phosphorus tribromide (0.253 mL, 2.67 mmol) was added to a solution ofC22 (134 mg, 0.542 mmol) in dichloromethane (10 mL), and the reactionwas allowed to stir at RT for 2 hours. It was then partitioned betweencold water and additional dichloromethane, and the organic layer waswashed with water, washed with brine, dried over magnesium sulfate,filtered and concentrated in vacuo. Purification using silica gelchromatography (Eluant: 30% EtOAc in heptane) afforded C23 as acolorless oil. Yield: 143 mg, 0.461 mmol, 85%. LCMS m/z 312.0 (M+1). ¹HNMR (400 MHz, CDCl₃) δ 3.75 (s, 3H), 4.13 (br s, 2H), 4.69 (s, 2H),7.11-7.15 (m, 2H), 7.28-7.33 (m, 1H), 7.33-7.38 (m, 2H).

Step 5. Synthesis of tert-butyl3-(5-benzyl-1-methyl-3-nitro-1H-pyrazol-4-yl)-N-(diphenylmethylene)-L-alaninate(C24)

C23 was converted to C24 according to the general procedure for thesynthesis of C5 in Example 1. C24 was obtained as a colorless glass.Yield: 194 mg, 0.370 mmol, 80%. LCMS m/z 525.3 (M+1). ¹H NMR (400 MHz,CDCl₃) δ 1.44 (s, 9H), 3.24 (dd, J=14.0, 9.8 Hz, 1H), 3.52 (dd, J=14.0,4.0 Hz, 1H), 3.63 (s, 3H), 3.86 (d, J=17.0 Hz, 1H), 4.27 (d, J=17.1 Hz,1H), 4.36 (dd, J=9.7, 4.0 Hz, 1H), 6.70-6.77 (m, 2H), 6.97-7.02 (m, 2H),7.20-7.25 (m, 3H), 7.31-7.44 (m, 6H), 7.60-7.64 (m, 2H).

Step 6. Synthesis of3-(5-benzyl-1-methyl-3-nitro-1H-pyrazol-4-yl)-L-alanine, HCl salt (C25)

Concentrated HCl (12 M, 0.156 mL, 1.87 mmol) was slowly added to asolution of C24 (194 mg, 0.370 mmol) in acetonitrile (10 mL), and thereaction was heated at 50° C. for 4 hours. After removal of solvent invacuo, the residue was partitioned between diethyl ether (50 mL) andwater (10 mL), and the aqueous layer was washed twice with diethylether. Concentration of the aqueous layer under reduced pressureprovided C25 as a colorless solid. Yield: 125 mg, 0.367 mmol, 99%. LCMSm/z 305.1 (M+1). ¹H NMR (400 MHz, CD₃OD) δ 3.28 (dd, J=14.6, 7.0 Hz, 1H,assumed; partially obscured by solvent peak), 3.50 (dd, J=14.6, 7.8 Hz,1H), 3.77 (s, 3H), 4.04 (dd, J=7.4, 7.4 Hz, 1H), 4.20 (AB quartet,J_(AB)=17.1 Hz, Δν_(AB)=22.9 Hz, 2H), 7.11-7.15 (m, 2H), 7.24-7.29 (m,1H), 7.32-7.37 (m, 2H).

Step 7. Synthesis of3-(5-benzyl-1-methyl-3-nitro-1H-pyrazol-4-yl)-N-(tert-butoxycarbonyl)-L-alanine(C26)

Di-tert-butyl dicarbonate (96.9 mg, 0.444 mmol) was added to a solutionof C25 (125 mg, 0.367 mmol) and triethylamine (0.208 mL, 1.48 mmol) inwater (10 mL), and the reaction was allowed to stir at RT for 18 hours.After acidification of the reaction mixture to pH˜5 with 10% aqueouscitric acid solution, it was extracted with EtOAc. The combined organiclayers were washed with water, dried over magnesium sulfate, filteredand concentrated in vacuo to provide C26 as a pale yellow foam (150 mg),which was taken directly to the following step. LCMS m/z 403.1 (M−1). ¹HNMR (400 MHz, CD₃OD) δ 1.36 (br s, 9H), 3.05 (br dd, J=14.0, 9.6 Hz,1H), 3.40 (br dd, J=14.2, 5.5 Hz, 1H), 3.68 (s, 3H), 4.17 (br ABquartet, J_(AB)=17.2 Hz, Δν_(AB)=30 Hz, 2H), 4.42 (br dd, J=9.4, 5.5 Hz,1H), 7.10-7.16 (m, 2H), 7.22-7.27 (m, 1H), 7.29-7.35 (m, 2H).

Step 8. Synthesis of 2,2,2-trifluoroethyl3-(5-benzyl-1-methyl-3-nitro-1H-pyrazol-4-yl)-N-(tert-butoxycarbonyl)-L-alaninate(C27)

Trifluoroethyl trifluoromethanesulfonate (112 mg, 0.483 mmol) was addedto a solution of C26 (≦0.367 mmol) and triethylamine (0.13 mL, 0.93mmol) in tetrahydrofuran (10 mL), and the mixture was heated at 60° C.for 18 hours. After cooling, the reaction mixture was partitionedbetween EtOAc and water. The organic layer was washed with water, washedwith brine, dried over magnesium sulfate, filtered and then concentratedin vacuo to afford C27 as an oil. Yield: 135 mg, 0.278 mmol, 76% fromstep 7. LCMS m/z 385.0 [(M-CO₂ and 2-methylprop-1-ene)-1]. ¹H NMR (400MHz, CDCl₃) δ 1.38 (br s, 9H), 3.24-3.36 (m, 2H), 3.73 (s, 3H),4.03-4.15 (m, 2H), 4.44-4.57 (m, 3H), 5.16 (br d, J=8 Hz, 1H), 7.04 (brd, J=7.2 Hz, 2H), 7.25-7.36 (m, 3H).

Step 9. Synthesis of tert-butyl[(5S)-3-benzyl-7-hydroxy-2-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridin-5-yl]carbamate(C28)

C27 was converted to C28 according to the general procedure for thesynthesis of C9 in Example 1. C28 was obtained as a colorless solid.Yield: 71 mg, 0.19 mmol, 68%. LCMS m/z 373.2 (M+1). ¹H NMR (400 MHz,CD₃OD) δ 1.46 (s, 9H), 2.57 (dd, J=15.0, 13.3 Hz, 1H), 2.79 (br dd,J=15, 7 Hz, 1H), 3.63 (s, 3H), 4.02 (s, 2H), 4.42 (br dd, J=13, 7 Hz,1H), 7.15-7.19 (m, 2H), 7.21-7.26 (m, 1H), 7.29-7.34 (m, 2H).

Step 10. Synthesis of Example 3

C28 (68 mg, 0.18 mmol) was combined with a solution of HCl in1,4-dioxane (4 M, 2 mL, 8 mmol), and the reaction was allowed to stir atRT for 45 minutes. After concentration of the reaction in vacuo, thesolid residue was slurried in diethyl ether to provide a sticky solid.This was dissolved in methanol and concentrated in vacuo, affording asolid for Example 3. Yield: 49 mg, 0.16 mmol, 88%. LCMS m/z 273.2 (M+1).¹H NMR (400 MHz, CD₃OD) δ 2.65 (dd, J=14, 14 Hz, 1H), 2.93 (dd, J=14.5,7.4 Hz, 1H), 3.68 (s, 3H), 4.07 (AB quartet, J_(AB)=16.5 Hz,Δν_(AB)=13.4 Hz, 2H), 4.35 (dd, J=13.5, 7.5 Hz, 1H), 7.18-7.21 (m, 2H),7.23-7.28 (m, 1H), 7.31-7.36 (m, 2H).

Example 4(6S)-6-Amino-1-benzyl-4-hydroxy-1,4,6,7-tetrahydro-5H-pyrazolo[4,3-b]pyridin-5-one,HCl salt (4)

Step 1. Synthesis of methyl 4-nitro-1H-pyrazole-3-carboxylate (C29)

Fuming sulfuric acid (4 mL) was added to a solution of4-nitro-1H-pyrazole-3-carboxylic acid (16.0 g, 102 mmol) in methanol(200 mL), and the reaction was stirred at RT for 24 hours. The reactionmixture was concentrated, and the resulting solid was partitionedbetween EtOAc and water. The aqueous layer was extracted twice withEtOAc, and the combined organic layers were dried over magnesiumsulfate, filtered and concentrated in vacuo, providing C29 as a whitesolid. Yield: 17.1 g, 99.9 mmol, 98%. LCMS m/z 170.0 (M−1). ¹H NMR (400MHz, CDCl₃) δ 4.05 (s, 3H), 8.40 (s, 1H).

Step 2. Synthesis of methyl 1-benzyl-4-nitro-1H-pyrazole-5-carboxylate(C30)

To a solution of C29 (17.1 g, 99.9 mmol) in acetone (500 mL) was addedbenzyl bromide (11.8 mL, 99.8 mmol) and potassium carbonate (13.8 g,99.8 mmol), and the reaction was heated at reflux for 2.25 hours.Solvent was removed in vacuo, and the residue was partitioned betweenwater and dichloromethane. The aqueous layer was extracted twice withdichloromethane, and the combined organic layers were dried overmagnesium sulfate, filtered and concentrated under reduced pressure. Theresulting oil was combined with material derived from a very similarreaction carried out on 28 mmol of C29, and purification was effectedvia silica gel chromatography (Gradient: 0% to 40% EtOAc in heptane).The less polar isomer was collected to provide C30 as an oil. Yield:7.07 g, 27.1 mmol, 21%. The regiochemistry of C30 was assigned based onNOE studies carried out on C30 and the regioisomeric, more polarmaterial from the chromatography. ¹H NMR (400 MHz, CDCl₃) δ 3.92 (s,3H), 5.49 (s, 2H), 7.24-7.28 (m, 2H), 7.34-7.39 (m, 3H), 8.07 (s, 1H).

Step 3. Synthesis of (1-benzyl-4-nitro-1H-pyrazol-5-yl)methanol (C31)

Sodium borohydride (1.44 g, 38.0 mmol) was added to a solution of C30(4.97 g, 19.0 mmol) in tetrahydrofuran (100 mL). The mixture was cooledto 0° C., and methanol (˜3.9 mL) was added drop-wise, at a rate suchthat effervescence was controlled. The reaction was then allowed to warmto RT and stirred at that temperature for 1 hour. After being quenchedwith water (1 mL), the reaction mixture was concentrated in vacuo. Theresidue was partitioned between dichloromethane and water, and theorganic layer was washed with brine, dried, filtered and evaporated toprovide C31 as a light pink solid. Yield: 4.08 g, 17.5 mmol, 92%. ¹H NMR(400 MHz, CD₃OD) δ 4.99 (s, 2H), 5.53 (s, 2H), 7.25-7.37 (m, 5H), 8.16(s, 1H).

Step 4. Synthesis of 1-benzyl-5-(bromomethyl)-4-nitro-1H-pyrazole (C32)

C31 was converted to C32 according to the general procedure for thesynthesis of C4 in Example 1. C32 was obtained as a white solid. Yield:1.69 g, 5.71 mmol, 66%. LCMS m/z 296.1 (M+1). ¹H NMR (400 MHz, CDCl₃) δ4.72 (s, 2H), 5.46 (s, 2H), 7.23-7.27 (m, 2H), 7.36-7.42 (m, 3H), 8.17(s, 1H).

Step 5. Synthesis of tert-butyl3-(1-benzyl-4-nitro-1H-pyrazol-5-yl)-N-(diphenylmethylene)-L-alaninate(C33)

C32 was converted to C33 according to the general procedure for thesynthesis of C5 in Example 1. C33 was obtained as an oil. Yield: 1.29 g,2.53 mmol, 72%. LCMS m/z 511.3 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 1.47 (s,9H), 3.50 (dd, J=14.2, 10.2 Hz, 1H), 3.71 (dd, J=14.1, 3.6 Hz, 1H), 4.45(dd, J=10.2, 3.7 Hz, 1H), 5.28 (d, J=15.5 Hz, 1H), 5.64 (d, J=15.5 Hz,1H), 6.72-6.76 (m, 2H), 7.15-7.19 (m, 2H), 7.30-7.45 (m, 9H), 7.60-7.64(m, 2H), 8.10 (s, 1H).

Step 6. Synthesis of 3-(1-benzyl-4-nitro-1H-pyrazol-5-yl)-L-alanine, HClsalt (C34)

C33 (652 mg, 1.28 mmol) was converted to C34 according to the generalprocedure for the synthesis of C25 in Example 3. C34 was obtained as awhite solid, which was carried directly into the next step. LCMS m/z291.2 (M+1). ¹H NMR (400 MHz, CD₃OD) δ 3.59 (dd, half of ABX pattern,J=14.8, 6.7 Hz, 1H), 3.71 (dd, half of ABX pattern, J=14.7, 8.4 Hz, 1H),4.12 (dd, J=8.2, 6.8 Hz, 1H), 5.49 (AB quartet, J_(AB)=15.9 Hz,Δν_(AB)=24.4 Hz, 2H), 7.21-7.25 (m, 2H), 7.33-7.40 (m, 3H), 8.27 (s,1H).

Step 7. Synthesis of 2,2,2-trifluoroethyl3-(1-benzyl-4-nitro-1H-pyrazol-5-yl)-N-(tert-butoxycarbonyl)-L-alaninate(C35)

C34 was converted to C35 according to the general procedures for thetransformation of C16 to C18 in Example 2. C35 was obtained as a whitesolid. Yield: 448 mg, 0.948 mmol, 74% from step 6. LCMS m/z 373.1[(M-CO₂ and 2-methylprop-1-ene)+1]. ¹H NMR (400 MHz, CDCl₃) δ 1.43 (s,9H), 3.54 (d, J=7.2 Hz, 2H), 4.39-4.61 (m, 3H), 5.26 (br d, J=7 Hz, 1H),5.46 (AB quartet, 2 downfield peaks are broad, J_(AB)=15.6 Hz,Δν_(AB)=34 Hz, 2H), 7.20-7.25 (m, 2H), 7.32-7.39 (m, 3H), 8.16 (s, 1H).

Step 8. Synthesis of tert-butyl[(6S)-1-benzyl-4-hydroxy-5-oxo-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-b]pyridin-6-yl]carbamate(C36)

C35 was converted to C36 according to the general procedure for thesynthesis of C9 in Example 1. C36 was obtained as a white solid. Yield:32 mg, 0.089 mmol, 10%; the yield was 32% based on recovered startingmaterial. LCMS m/z 359.2 (M+1). ¹H NMR (400 MHz, CD₃OD) δ 1.45 (s, 9H),2.81 (br dd, J=16, 13 Hz, 1H), 3.24 (dd, J=15.8, 7.4 Hz, 1H), 4.53 (brdd, J=13, 7.5 Hz, 1H), 5.30 (s, 2H), 7.15-7.19 (m, 2H), 7.26-7.38 (m,3H), 7.37 (s, 1H).

Step 9. Synthesis of Example 4

C36 was converted to Example 4 according to the general procedure forthe synthesis of 3 in Example 3. Example 4 was obtained as a solid.Yield: 27 mg, quantitative. LCMS m/z 241.3 [(M-H₂O)+1). ¹H NMR (400 MHz,CD₃OD) δ 2.90 (dd, J=15.4, 13.7 Hz, 1H), 3.38 (dd, J=15.3, 7.8 Hz, 1H),4.48 (dd, J=13.5, 7.9 Hz, 1H), 5.35 (AB quartet, J_(AB)=15.8 Hz,Δν_(AB)=16.7 Hz, 2H), 7.18-7.21 (m, 2H), 7.30-7.39 (m, 3H), 7.45 (s,1H).

Example 5(6S)-6-Amino-1-benzyl-4-hydroxy-3-(trifluoromethyl)-1,4,6,7-tetrahydro-5H-pyrazolo[4,3-b]pyridin-5-one,HCl salt (5)

Step 1. Synthesis of4-nitro-5-(trifluoromethyl)-1H-pyrazole-3-carboxylic acid (C37)

Potassium permanganate (56.7 g, 359 mmol) was added to a solution of3-methyl-4-nitro-5-(trifluoromethyl)-1H-pyrazole (prepared from3-methyl-5-(trifluoromethyl)-1H-pyrazole as described by B. A. Acker etal., PCT Int. Appl. 2006, WO 2006046135; 20.0 g, 102.5 mmol) in water(400 mL), and the reaction mixture was heated at 100° C. for 12 hours.The mixture was passed through a pad of Celite, and the filtrate wasacidified with concentrated HCl, then extracted with EtOAc. The combinedorganic layers were dried over sodium sulfate, filtered and concentratedin vacuo to afford C37 as a white solid. Yield: 20.0 g, 88.9 mmol, 87%.LCMS m/z 224.0 (M−1). ¹³C NMR (75 MHz, DMSO-d₆) δ 119.5 (q, J_(cF)=269Hz), 130.9, 133.7, 134.4 (q, J_(cF)=39 Hz), 157.4.

Step 2. Synthesis of ethyl4-nitro-5-(trifluoromethyl)-1H-pyrazole-3-carboxylate (C38)

A solution of C37 (20.0 g, 88.9 mmol) in ethanol (200 mL) was cooled to0° C. HCl gas was bubbled through the reaction mixture for 1 hour, andthen the reaction was warmed to RT and allowed to stir for 12 hours. Themixture was cooled to 0° C., and treated with HCl gas in the same mannerfor 1 hour. It was again warmed to RT and stirred for an additional 12hours, at which time it was concentrated in vacuo and diluted withdichloromethane. After being washed with water, the organic layer wasdried over sodium sulfate, filtered and concentrated under reducedpressure. The resulting material was triturated with pentane to affordC38 as a white solid. Yield: 12.0 g, 47.4 mmol, 53%. LCMS m/z 252.0(M−1). ¹H NMR (300 MHz, CDCl₃) δ 1.43 (t, J=7.1 Hz, 3H), 4.52 (q, J=7.1Hz, 2H), 11.66 (br s, 1H).

Step 3. Synthesis of ethyl1-benzyl-4-nitro-3-(trifluoromethyl)-1H-pyrazole-5-carboxylate (C39)

C38 was converted to C39 according to the general procedure for thesynthesis of C2 in Example 1, except that the reaction was only allowedto proceed for 2 hours. C39, the major regioisomer, was obtained as ayellow liquid. The regiochemistry of alkylation was assigned based on anHMBC experiment carried out on C39. Yield: 5.0 g, 15 mmol, 74%. GCMS m/z343.1 (M). ¹H NMR (300 MHz, CDCl₃) δ 1.29 (t, J=7.1 Hz, 3H), 4.37 (q,J=7.1 Hz, 2H), 5.60 (s, 2H), 7.28-7.41 (m, 5H).

Step 4. Synthesis of[1-benzyl-4-nitro-3-(trifluoromethyl)-1H-pyrazol-5-yl]methanol (C40)

C39 was converted to C40 according to the general procedure for thesynthesis of C31 in Example 4. Upon completion of the reaction, in thiscase the reaction mixture was concentrated in vacuo, and the residue waspartitioned between EtOAc and 1 N aqueous HCl. The organic layer wasdried over sodium sulfate, filtered and concentrated. Purification waseffected via silica gel chromatography (Eluant: 10% EtOAc in petroleumether) to afford C40 as a yellow solid. Yield: 3.5 g, 12 mmol, 80%. GCMSm/z 301.1 (M). ¹H NMR (400 MHz, CDCl₃) δ 2.63 (t, J=7.2 Hz, 1H), 4.93(d, J=7.1 Hz, 2H), 5.53 (s, 2H), 7.25-7.29 (m, 2H, assumed; partiallyobscured by solvent peak), 7.36-7.43 (m, 3H).

Step 5. Synthesis of1-benzyl-5-(bromomethyl)-4-nitro-3-(trifluoromethyl)-1H-pyrazole (C41)

Carbon tetrabromide (0.80 g, 2.4 mmol) and triphenylphosphine (0.70 g,2.7 mmol) were added to a 0° C. solution of C40 (0.40 g, 1.3 mmol) indichloromethane (40 mL), and the reaction was allowed to stir at 0° C.for 30 minutes. After being washed with water, the reaction mixture wasdried over sodium sulfate, filtered, and concentrated under reducedpressure. Silica gel chromatography (Eluant: 5% EtOAc in petroleumether) afforded C41 as a yellow oil. Yield: 0.44 g, 1.2 mmol, 92%. ¹HNMR (400 MHz, CDCl₃) δ 4.67 (s, 2H), 5.52 (s, 2H), 7.26-7.30 (m, 2H,assumed; partially obscured by solvent peak), 7.37-7.45 (m, 3H).

Step 6. Synthesis of tert-butyl3-[1-benzyl-4-nitro-3-(trifluoromethyl)-1H-pyrazol-5-yl]-N-(diphenylmethylene)-L-alaninate(C42)

To a solution of C41 (595 mg, 1.63 mmol) in dichloromethane (13 mL) wasadded tert-butyl N-(diphenylmethylene)glycinate (98%, 640 mg, 2.12 mmol)and O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (95%, 104 mg,0.163 mmol). The mixture was cooled to −30° C., and cesium hydroxide(357 mg, 2.12 mmol) was added; the reaction was allowed to stir at −30°C. for 16 hours. The reaction was quenched at −30° C. with aqueousammonium chloride solution, allowed to warm to RT and then extractedtwice with dichloromethane. The combined organic layers were washed withwater, dried over magnesium sulfate, filtered and concentrated in vacuo.Purification using silica gel chromatography (Gradient: 5% to 25% EtOAcin heptanes) provided C42 as a yellow oil. Yield: 154 mg, 0.266 mmol,16%. LCMS m/z 579.3 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 1.48 (s, 9H), 3.49(dd, J=14.2, 10.3 Hz, 1H), 3.68 (dd, J=14.2, 3.5 Hz, 1H), 4.44 (dd,J=10.2, 3.4 Hz, 1H), 5.31 (d, J=15.4 Hz, 1H), 5.73 (d, J=15.5 Hz, 1H),6.67-6.72 (m, 2H), 7.19-7.24 (m, 2H), 7.32-7.47 (m, 9H), 7.60-7.66 (m,2H).

Step 7. Synthesis of3-[1-benzyl-4-nitro-3-(trifluoromethyl)-1H-pyrazol-5-yl]-L-alanine, HClsalt (C43)

C42 (120 mg, 0.207 mmol) was treated with a solution of HCl in1,4-dioxane (4 M, 5 mL), and the reaction mixture was heated to 100° C.for 2 hours. It was then concentrated in vacuo, and the residue wasdiluted with 1 M aqueous HCl. After being washed with diethyl ether, theaqueous layer was concentrated to provide crude C43 as an off-whitesolid. Yield: 60 mg, 0.15 mmol, 72%. APCI m/z 358.9 (M+1). ¹H NMR (300MHz, DMSO-d₆) δ 3.52-3.73 (m, 1H), 3.77-3.90 (m, 1H), 4.14-4.26 (m, 1H),5.64 (AB quartet, 2 downfield peaks are broad, J_(AB)=16 Hz, Δν_(AB)=50Hz, 2H), 7.26-7.44 (m, 5H), 8.73 (br s, 3H).

Step 8. Synthesis of3-[1-benzyl-4-nitro-3-(trifluoromethyl)-1H-pyrazol-5-yl]-N-(tert-butoxycarbonyl)-L-alanine(C44)

C43 was converted to C44 according to the general procedure for thesynthesis of C17 in Example 2. In this case, the reaction was carriedout for 30 minutes, and at that point, the reaction mixture wasconcentrated in vacuo. The residue was mixed with aqueous ammoniumchloride solution and extracted with EtOAc. The combined organic layerswere dried over sodium sulfate, filtered and concentrated under reducedpressure. The residue was triturated with n-pentane to provide C44 as anoff-white solid. Yield: 0.80 g, 1.7 mmol, 91%. LCMS m/z 457.0 (M−1). ¹HNMR (300 MHz, DMSO-d₆) δ 1.26 (br s, 9H), 3.10-3.23 (m, 1H), 3.52-3.62(m, 1H), 4.00-4.13 (m, 1H), 5.56 (AB quartet, J_(AB)=15.8 Hz,Δν_(AB)=40.1 Hz, 2H), 6.37 (br s, 1H), 7.22-7.29 (m, 2H), 7.31-7.42 (m,3H).

Step 9. Synthesis of 2,2,2-trifluoroethyl3-[1-benzyl-4-nitro-3-(trifluoromethyl)-1H-pyrazol-5-yl]-N-(tert-butoxycarbonyl)-L-alaninate(C45)

C44 was converted to C45 according to the general procedure for thesynthesis of C18 in Example 2, except that in this case, the reactionwas carried out at 50° C. for 18 hours, and crude C45 was taken on tothe next step without chromatographic purification. Yield: 35 mg, 0.065mmol, 77%. ¹H NMR (400 MHz, CDCl₃) δ 1.43 (s, 9H), 3.48-3.60 (m, 2H),4.39-4.63 (m, 3H), 5.25 (br d, J=7 Hz, 1H), 5.54 (AB quartet, 2downfield peaks are broad, J_(AB)=15.4 Hz, Δν_(AB)=36 Hz, 2H), 7.24-7.29(m, 2H), 7.31-7.41 (m, 3H).

Step 10. Synthesis of tert-butyl[(6S)-1-benzyl-4-hydroxy-5-oxo-3-(trifluoromethyl)-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-b]pyridin-6-yl]carbamate(C46)

C45 was converted to C46 according to the general procedure for thesynthesis of C9 in Example 1. The final material was azeotroped withheptane to remove the last traces of pyridine, providing C46 as a whitesolid. Yield: 16 mg, 0.038 mmol, 58%. LCMS m/z 427.2 (M+1). ¹H NMR (400MHz, CD₃OD) δ 1.45 (s, 9H), 2.81 (dd, J=15.6, 13.6 Hz, 1H), 3.26 (dd,J=15.8, 7.3 Hz, 1H), 4.56 (br dd, J=13.3, 7.5 Hz, 1H), 5.35 (s, 2H),7.20-7.24 (m, 2H), 7.29-7.39 (m, 3H).

Step 11. Synthesis of Example 5

C46 was converted to Example 5 according to the general procedure forthe synthesis of 3 in Example 3. After isolation, the product wasazeotroped once with methanol, twice with 2-propanol and once withheptane, affording a solid for Example 5. Yield: 10 mg, 0.028 mmol, 69%.LCMS m/z 327.2 (M+1). ¹H NMR (400 MHz, CD₃OD) δ 2.92 (dd, J=15.4, 13.8Hz, 1H), 3.41 (dd, J=15.4, 7.8 Hz, 1H), 4.54 (dd, J=13.7, 7.8 Hz, 1H),5.41 (AB quartet, J_(AB)=15.6 Hz, Δν_(AB)=16.4 Hz, 2H), 7.22-7.26 (m,2H), 7.32-7.41 (m, 3H).

Example 6(5S)-5-Amino-7-hydroxy-2-[4-(trifluoromethoxy)benzyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one,HCl salt (6)

Step 1. Synthesis of ethyl3-nitro-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazole-4-carboxylate (C47)

3,4-Dihydro-2H-pyran (95%, 8.66 mL, 90.8 mmol) was added to a solutionof C1 (11.2 g, 60.5 mmol) and para-toluenesulfonic acid monohydrate(96%, 3.00 g, 15.1 mmol) in dichloromethane (120 mL), and the reactionwas stirred for 20 minutes at RT. The mixture was washed with aqueoussodium bicarbonate solution, then with brine, dried over sodium sulfate,filtered, and concentrated in vacuo to provide C47 as an oil (18 g),which was taken directly into the following reaction without additionalpurification. The regiochemistry of C47 was supported by an NOEexperiment: irradiation of the pyrazole CH resulted in enhancement ofthe tetrahydropyran methine signal. ¹H NMR (400 MHz, CDCl₃) δ 1.34 (t,J=7.1 Hz, 3H), 1.47-1.76 (m, 3H), 1.93-2.04 (m, 2H), 2.14-2.21 (m, 1H),3.68-3.76 (m, 1H), 4.02-4.09 (m, 1H), 4.33 (q, J=7.2 Hz, 2H), 5.42 (dd,J=8.6, 2.9 Hz, 1H), 8.13 (s, 1H).

Step 2. Synthesis of[3-nitro-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazol-4-yl]methanol (C48)

C47 was converted to C48 according to the general procedure for thesynthesis of C3 in Example 1. C48 was obtained as an oil (15.7 g), whichwas taken directly to the next step without further purification. ¹H NMR(400 MHz, CDCl₃) δ 1.49-1.78 (m, 3H), 1.97-2.08 (m, 2H), 2.12-2.19 (m,1H), 3.68-3.76 (m, 1H), 4.03-4.09 (m, 1H), 4.82-4.83 (m, 2H), 5.43 (dd,J=8.8, 2.9 Hz, 1H), 7.75-7.76 (m, 1H).

Step 3. Synthesis of4-(bromomethyl)-3-nitro-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazole (C49)

Triphenylphosphine (27.0 g, 103 mmol) and carbon tetrabromide (34.5 g,103 mmol) were added to a solution of C48 (≦60.5 mmol) indichloromethane (300 mL), and the reaction was allowed to stir at RT for15 minutes. The reaction mixture was concentrated in vacuo and purifiedvia silica gel chromatography (Gradient: 10% to 50% EtOAc in heptane) toprovide C49 as a light orange oil. Yield: 10.6 g, 36.5 mmol, 60% fromstep 1. ¹H NMR (400 MHz, CDCl₃) δ 1.62-1.76 (m, 3H), 1.95-2.05 (m, 2H),2.14-2.21 (m, 1H), 3.68-3.76 (m, 1H), 4.03-4.09 (m, 1H), 4.66 (s, 2H),5.42 (dd, J=8.9, 2.8 Hz, 1H), 7.83 (s, 1H).

Step 4. Synthesis of tert-butylN-(diphenylmethylene)-3-[3-nitro-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazol-4-yl]-L-alaninate(C50)

C49 was converted to C50 according to the general procedure for thesynthesis of C5 in Example 1. C50 was obtained as a solid, judged to bea roughly 1:1 mixture of diastereomers from the proton NMR spectrum.Yield: 14.9 g, 29.5 mmol, 81%. ¹H NMR (400 MHz, CDCl₃) δ 1.42 and 1.44(2 s, 9H), 1.51-1.72 (m, 3H), 1.82-2.10 (m, 3H), 3.25-3.33 (m, 1H),3.38-3.47 (m, 1H), 3.55-3.69 (m, 1H), 3.86-3.98 (m, 1H), 4.22-4.29 (m,1H), 5.33-5.39 (m, 1H), 6.83-6.89 and 6.90-6.96 (2 m, 2H), 7.28-7.34 (m,2H), 7.36-7.42 (m, 4H), 7.57-7.66 (m, 3H).

Step 5. Synthesis of 3-(3-nitro-1H-pyrazol-4-yl)-L-alanine, HCl salt(C51)

C50 (14.8 g, 29.3 mmol) was treated with a solution of HCl in1,4-dioxane (4 M, 200 mL), and the reaction was heated at 100° C. for 2hours. The reaction mixture was then concentrated in vacuo and treatedwith diethyl ether and 1 M aqueous HCl. The aqueous phase wasconcentrated under reduced pressure to provide a solid; NMR analysisindicated that some tetrahydropyran-protected compound was stillpresent. The solid was therefore resubjected to the reaction conditionsfor an additional 1.5 hours. After removal of solvent in vacuo, theresidue was treated with diethyl ether and 1 M aqueous HCl. The aqueouslayer was evaporated to provide C51 as a solid (7.1 g), which was useddirectly in the following step without additional purification. LCMS m/z199.1 (M−1). ¹H NMR (400 MHz, CD₃OD) δ 3.32 (dd, J=14.9, 7.6 Hz, 1H,assumed; partially obscured by solvent peak), 3.57 (br dd, J=14.9, 6.0Hz, 1H), 4.30 (dd, J=7.6, 6.1 Hz, 1H), 7.82 (s, 1H).

Step 6. Synthesis of tert-butyl4-[(2S)-2-[(tert-butoxycarbonyl)amino]-3-oxo-3-(2,2,2-trifluoroethoxy)propyl]-3-nitro-1H-pyrazole-1-carboxylate(C52)

C51 was converted to C52 according to the general procedures for theconversion of C16 to C18 in Example 2. C52 was obtained as a white solidfoam. Yield: 8.0 g, 17 mmol, 57% from step 5. LCMS m/z 381.1 [(M-CO₂ and2-methylprop-1-ene)-1]. ¹H NMR (400 MHz, CDCl₃) δ 1.40 (s, 9H), 1.66 (s,9H), 3.22 (dd, J=14.7, 7.9 Hz, 1H), 3.44 (dd, J=14.8, 5.1 Hz, 1H),4.46-4.63 (m, 2H), 4.63-4.71 (m, 1H), 5.15 (br d, J=7.4 Hz, 1H), 8.06(s, 1H).

Step 7. Synthesis of tert-butyl(5S)-5-[(tert-butoxycarbonyl)amino]-7-hydroxy-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-2-carboxylate(C53)

C52 was converted to C53 according to the general procedure for thepreparation of C9 in Example 1. C53 was obtained as a white solid.Yield: 3.6 g, 9.8 mmol, 68%. LCMS m/z 369.0 (M+1). ¹H NMR (400 MHz,CDCl₃) δ 1.46 (s, 9H), 1.65 (s, 9H), 2.58 (br dd, J=14, 14 Hz, 1H),3.33-3.47 (m, 1H), 4.38-4.51 (m, 1H), 5.58-5.68 (m, 1H), 7.78 (s, 1H),9.76 (br s, 1H).

Step 8. Synthesis of tert-butyl{(5S)-6-oxo-7-[(triisopropylsilyl)oxy]-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridin-5-yl}carbamate(C54)

A solution of C53 (250 mg, 0.679 mmol) in methanol (10 mL) was treatedwith lithium hydroxide hydrate (57.0 mg, 1.36 mmol), and the reactionwas stirred for 15 minutes. Solvent was removed under reduced pressureat RT, and the residue was partitioned between EtOAc and water. Theaqueous phase was concentrated in vacuo at 30° C. to provide themono-deprotected intermediate as a light orange solid (130 mg) [LCMS m/z269.1 (M+1)]. A portion of this material (80 mg) was dissolved inN,N-dimethylformamide (3 mL) and treated with triisopropylsilyl chloride(97%, 0.276 mL, 1.26 mmol) and imidazole (86.1 mg, 1.26 mmol). Thereaction mixture was allowed to stir for 1 hour at RT, then was dilutedwith diethyl ether and washed with water. The organic layer was washedwith saturated aqueous lithium chloride solution and with saturatedaqueous sodium bicarbonate solution, then concentrated in vacuo.Purification via silica gel chromatography (Gradient: 30% to 40% EtOAcin heptane) provided C54 as a white solid. Yield: 75 mg, 0.18 mmol, 42%.LCMS m/z 425.3 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 1.16 (d, J=7.5 Hz, 9H),1.17 (d, J=7.5 Hz, 9H), 1.34-1.46 (m, 3H), 1.47 (s, 9H), 2.50 (br dd,J=14, 14 Hz, 1H), 3.42 (br dd, J=14, 7 Hz, 1H), 4.36-4.45 (m, 1H),5.74-5.81 (m, 1H), 7.24-7.26 (m, 1H), 9.79 (br s, 1H).

Step 9. Synthesis of tert-butyl{(5S)-6-oxo-2-[4-(trifluoromethoxy)benzyl]-7-[(triisopropylsilyl)oxy]-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridin-5-yl}carbamate(C55)

1-(Bromomethyl)-4-(trifluoromethoxy)benzene (144 mg, 0.565 mmol),potassium iodide (3.8 mg, 0.023 mmol) and potassium carbonate (99%, 47.3mg, 0.339 mmol) were added to a solution of C54 (48 mg, 0.11 mmol) inN,N-dimethylformamide (2 mL), and the reaction was stirred at RT for 66hours. After dilution with diethyl ether, the reaction mixture waswashed with water. The organic layer was washed with saturated aqueouslithium chloride solution, then concentrated in vacuo. Purificationusing silica gel chromatography (Gradient: 0% to 30% EtOAc in heptane)provided C55 as a colorless oil. Yield: 37 mg, 0.062 mmol, 56%. LCMS m/z599.4 (M+1). ¹H NMR (400 MHz, CDCl₃) δ 1.11 (d, J=7.6 Hz, 9H), 1.12 (d,J=7.6 Hz, 9H), 1.28-1.40 (m, 3H), 1.45 (s, 9H), 2.46 (br dd, J=14, 14Hz, 1H), 3.36 (br dd, J=14.5, 6.6 Hz, 1H), 4.33-4.42 (m, 1H), 5.14 (ABquartet, J_(AB)=15.0 Hz, Δν_(AB)=11.2 Hz, 2H), 5.73-5.80 (m, 1H), 7.10(s, 1H), 7.15-7.20 (m, 2H), 7.23-7.27 (m, 2H).

Step 10. Synthesis of Example 6

C55 (36 mg, 0.060 mmol) was treated with a solution of HCl in1,4-dioxane (4 M, 5 mL), and the reaction was allowed to stir for 2hours. The mixture was filtered, and the solid was washed with diethylether to provide a white solid for Example 6. Yield: 17 mg, 0.045 mmol,75%. LCMS m/z 343.0 (M+1). ¹H NMR (400 MHz, CD₃OD) δ 2.86 (ddd, J=14,14, 1.1 Hz, 1H), 3.25 (dd, J=14.6, 7.2 Hz, 1H), 4.40 (dd, J=13.7, 7.4Hz, 1H), 5.28 (s, 2H), 7.25 (br d, J=8 Hz, 2H), 7.39 (br d, J=8.6 Hz,2H), 7.62-7.63 (br s, 1H).

Example 7(5S)-5-Amino-7-hydroxy-2-[3-(trifluoromethyl)phenyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one,HCl salt (7)

Step 1. Synthesis of4-bromo-3-nitro-1-[3-(trifluoromethyl)phenyl]-1H-pyrazole (C56)

Pyridine (99%, 0.512 mL, 6.27 mmol) and[3-(trifluoromethyl)phenyl]boronic acid (649 mg, 3.42 mmol) were addedto a solution of 4-bromo-3-nitro-1H-pyrazole (596.6 mg, 3.108 mmol) intetrahydrofuran (9 mL); copper(II) acetate (99%, 855 mg, 4.66 mmol) wasthen added, and the reaction was stirred for 42 hours. The reactionmixture was filtered through Celite and concentrated in vacuo, thenpartitioned between EtOAc (5 mL) and water (5 mL). The aqueous layer wasextracted with EtOAc (3×5 mL), and the combined organic layers werewashed with water (5 mL) and dried over sodium sulfate. After filtrationand removal of solvent under reduced pressure, the residue was purifiedvia silica gel chromatography (Gradient: 0% to 20% EtOAc in heptane) toprovide C56. The regiochemistry of C56 was assigned based on NOEexperiments. Yield: 779 mg, 2.32 mmol, 75%. GCMS m/z 335, 337 (M⁺). ¹HNMR (400 MHz, CDCl₃) δ 7.68-7.76 (m, 2H), 7.94-7.98 (m, 1H), 7.99-8.01(m, 1H), 8.14 (s, 1H).

Step 2. Synthesis of methylN-(tert-butoxycarbonyl)-3-{3-nitro-1-[3-(trifluoromethyl)phenyl]-1H-pyrazol-4-yl}-L-alaninate(C57)

A dry vial was charged with zinc (99.5%, 494 mg, 7.52 mmol) andN,N-dimethylformamide (2 mL). Trimethylsilyl chloride (95%, 0.20 mL, 1.5mmol) was added, and the mixture was vigorously stirred for 30 minutes.The yellow supernatant was removed using a syringe, and the zinc waswashed with N,N-dimethylformamide (3×2 mL) until the liquid above thezinc was no longer colored. The activated zinc was then dried undervacuum with a heat gun until the zinc was free-flowing. The zinc wasallowed to cool to RT, then was treated with a solution of methylN-(tert-butoxycarbonyl)-3-iodo-L-alaninate (which may be preparedaccording to S. van Zutphen et al., Tetrahedron Lett. 2007, 48,2857-2859) (recrystallized from petroleum ether; 707 mg, 2.15 mmol) inN,N-dimethylformamide (2 mL); the reaction mixture became very hot. Themixture was stirred at RT until no starting material remained by thinlayer chromatographic analysis (about 30 minutes). The grey solution ofzinc adduct was transferred to a dry flask, and treated with C56 (602mg, 1.79 mmol), followed by palladium(II) acetate (4.00 mg, 0.0180 mmol)and 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (17.2 mg,0.0360 mmol). After 42 hours at RT, the reaction was filtered throughCelite, and the filter pad was washed with EtOAc (3×5 mL). Water (5 mL)was added to the combined filtrates, and the aqueous layer was extractedwith EtOAc (3×5 mL). The combined organic layers were washed with water(15 mL), dried over sodium sulfate, filtered and concentrated in vacuo.Purification via silica gel chromatography (0% to 40% EtOAc in heptane)provided C57, contaminated with some impurities (95 mg). This materialwas taken directly to the following step. LCMS m/z 359.1 [(M-CO₂ and2-methylprop-1-ene)+1]. ¹H NMR (400 MHz, CD₃OD), characteristic peaks: δ3.12 (dd, J=14.6, 9.7 Hz, 1H), 3.48 (dd, J=14.5, 5.1 Hz, 1H), 4.59(J=9.7, 4.9 Hz, 1H).

Step 3. Synthesis ofN-(tert-butoxycarbonyl)-3-{3-nitro-1-[3-(trifluoromethyl)phenyl]-1H-pyrazol-4-yl}-L-alanine(C58)

C57 was converted to C58 according to the general procedure for thesynthesis of C21 in Example 3. C58 was obtained as a solid (96 mg) stillcontaining impurities, which was taken directly to the next step. LCMSm/z 443.2 (M−1). ¹H NMR (400 MHz, CDCl₃), characteristic peaks: δ 3.11(dd, J=14.5, 9.8 Hz, 1H), 3.52 (dd, J=14.6, 4.8 Hz, 1H), 4.56 (dd,J=9.7, 4.6 Hz, 1H).

Step 4. Synthesis of 2,2,2-trifluoroethylN-(tert-butoxycarbonyl)-3-{3-nitro-1-[3-(trifluoromethyl)phenyl]-1H-pyrazol-4-yl}-L-alaninate(C59)

Compound C58 was converted to C59 according to the general procedure forthe synthesis of C27 in Example 3. In this case, purification wascarried out using silica gel chromatography (Gradient: 0% to 30% EtOAcin heptane), to provide C59 (98.9 mg) still containing impurities. Thismaterial was used directly in the next step. LCMS m/z 427.1 [(M-CO₂ and2-methylprop-1-ene)+1]. ¹H NMR (400 MHz, CDCl₃), characteristic peaks: δ3.30-3.39 (m, 1H), 3.52 (dd, J=14.9, 5.4 Hz, 1H), 4.49-4.66 (m, 2H).

Step 5. Synthesis of tert-butyl{(5S)-7-hydroxy-6-oxo-2-[3-(trifluoromethyl)phenyl]-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridin-5-yl}carbamate(C60)

Compound C59 was converted to C60 according to the general procedure forthe synthesis of C9 in Example 1. C60 was obtained as a solid. Yield:17.4 mg, 0.0422 mmol, 2% from step 2. LCMS m/z 357.3{[M-(2-methylprop-1-ene)]+1}. ¹H NMR (400 MHz, CD₃OD) δ 1.48 (s, 9H),2.84 (br dd, J=15, 14 Hz, 1H), 3.15 (dd, J=15.1, 7.1 Hz, 1H), 4.53 (brdd, J=13.3, 7.1 Hz, 1H), 7.54 (d, J=7.8 Hz, 1H), 7.65 (dd, J=8.0, 8.0Hz, 1H), 7.97 (br d, J=8 Hz, 1H), 8.04-8.07 (m, 1H), 8.17 (br s, 1H).

Step 6. Synthesis of Example 7

C60 (17.4 mg, 0.0422 mmol) was mixed with a solution of HCl in1,4-dioxane (4 M, 0.5 mL), and the reaction was stirred for 18 hours.Diethyl ether (2 mL) was added; the resulting product was collected byfiltration and washed with diethyl ether (3×3 mL) to provide anoff-white solid for Example 7. Yield: 11.7 mg, 0.0336 mmol, 80%. LCMSm/z 313.1 (M+1). ¹H NMR (400 MHz, CD₃OD) δ 2.96 (ddd, J=14.7, 13.7, 1.4Hz, 1H), 3.37 (dd, J=14.8, 7.4 Hz, 1H), 4.50 (dd, J=13.5, 7.4 Hz, 1H),7.59 (br d, J=7.9 Hz, 1H), 7.68 (br dd, J=8, 8 Hz, 1H), 7.98-8.02 (m,1H), 8.07-8.09 (m, 1H), 8.29 (d, J=1.1 Hz, 1H).

Making non-critical changes, the following compounds as provided inTable 1 were prepared using methods discussed herein:

TABLE 1 ¹H NMR (400 MHz, CD₃OD), Structure Method observed peaks, δ;LCMS, Ex and of Prepa- observed ion m/z (unless # IUPAC Name rationotherwise indicated)  8

  (5S)-5-amino-7-hydroxy-2-(1-naphthylmethyl)-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 ¹HNMR (300 MHz, DMSO-d₆) δ: 2.73 (br dd, J = 14, 14 Hz, 1H), 3.10 (br dd,J = 14, 7 Hz, 1H), 4.29-4.44 (m, 1H), 5.72 (s, 2H), 7.35 (br d, J = 7Hz, 1H), 7.50 (dd, J = 8.3, 7.1 Hz, 1H), 7.54-7.62 (m, 2H), 7.72 (s,1H), 7.90-8.00 (m, 2H), 8.17-8.21 (m, 1H), 8.52-8.66 (br m, 2H), 10.7 (vbr s, 1H); 309.3  9

  (5S)-5-amino-7-hydroxy-2-(2-naphthylmethyl)-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 ¹HNMR (400 MHz, DMSO-d₆) δ: 2.75 (dd, J = 14, 14 Hz, 1H), 3.12 (dd, J =15, 7 Hz, 1H), 4.34-4.44 (m, 1H), 5.39 (s, 2H), 7.42 (dd, J = 8.6, 1.4Hz, 1H), 7.49-7.56 (m, 2H), 7.78 (s, 1H), 7.81 (br s, 1H), 7.87-7.94 (m,3H), 8.51-8.62 (m, 2H), 10.7 (v br s, 1H); 309.0 10

  (5S)-5-amino-7-hydroxy-2-(2-methoxybenzyl)-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 ¹HNMR (300 MHz, DMSO-d₆) δ: 2.74 (br dd, J = 14, 14 Hz, 1H), 3.12 (dd, J =14.8, 7.3 Hz, 1H), 3.82 (s, 3H), 4.30-4.45 (m, 1H), 5.17 (s, 2H), 6.91(ddd, J = 7.5, 7.3, 1.0 Hz, 1H), 6.99-7.06 (m, 2H), 7.31 (ddd, J = 8.2,7.3, 1.7 Hz, 1H), 7.60 (br s, 1H), 8.54- 8.67 (m, 3H), 10.7 (v br s,1H); 289.2 11

  (5S)-5-amino-7-hydroxy-2-(3-methoxybenzyl)-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 ¹HNMR (300 MHz, DMSO-d₆) δ: 2.75 (br dd, J = 14, 14 Hz, 1H), 3.12 (dd, J =14.6, 7.3 Hz, 1H), 3.73 (s, 3H), 4.31-4.45 (m, 1H), 5.18 (s, 2H),6.80-6.90 (m, 3H), 7.26 (ddd, J = 8.0, 7.3, 0.8 Hz, 1H), 7.72 (s, 1H),8.53-8.67 (m, 3H), 10.72 (br s, 1H); 289.1 12

  (5S)-5-amino-2-benzyl-7-hydroxy-3-methyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 2.20(s, 3H), 2.78 (dd, J = 14, 14 Hz, 1H), 3.15 (dd, J = 14.3, 7.6 Hz, 1H),4.39 (dd, J = 13.6, 7.4 Hz, 1H), 5.26 (s, 2H), 7.14-7.18 (m, 2H),7.26-7.35 (m, 3H); 273.3 13

  (6S)-6-amino-2-benzyl-4-hydroxy-2,4,6,7-tetrahydro-5H-pyrazolo[4,3-b]pyridin-5- one, HCl salt Ex 3¹ 3.05 (dd, J= 15.0, 13.8 Hz, 1H), 3.34 (dd, J = 15.0, 7.5 Hz, 1H, assumed; partiallyobscured by solvent peak), 4.47 (dd, J = 13.8, 7.4 Hz, 1H), 5.27 (s,2H), 7.26- 7.37 (m, 5H), 7.63 (s, 1H); 259.1 14

  (5S)-5-amino-7-hydroxy-2-phenyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 3² 2.96 (ddd, J= 14, 14, 1.2 Hz, 1H), 3.36 (dd, J = 14.6, 7.4 Hz, 1H), 4.48 (dd, J =13.7, 7.2 Hz, 1H), 7.30 (br t, J = 7.4 Hz, 1H), 7.47 (br dd, J = 8.6,7.4 Hz, 2H), 7.70-7.73 (m, 2H), 8.14 (d, J = 1 Hz, 1H); 245.2 15

  (5S)-5-amino-7-hydroxy-2-(4-methoxybenzyl)-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 2.83(ddd, J = 14, 14, 1 Hz, 1H), 3.21 (dd, J = 14.5, 7.4 Hz, 1H), 3.77 (s,3H), 4.38 (dd, J = 13.9, 7.3 Hz, 1H), 5.15 (s, 2H), 6.89 (br d, J = 8.7Hz, 2H), 7.24 (br d, J = 8.5 Hz, 2H), 7.51-7.52 (br s, 1H); 289.1 16

  6-amino-4-hydroxy-2-phenyl-2,4,6,7-tetrahydro-5H-pyrazolo[4,3-b]pyridin-5- one, HCl salt Ex 1³ 3.16 (br dd,J = 15, 14 Hz, 1H), 3.48 (dd, J = 15.2, 7.4 Hz, 1H), 4.55 (br dd, J =14, 7 Hz, 1H), 7.32 (br t, J = 8 Hz, 1H), 7.48 (br dd, J = 8, 8 Hz, 2H),7.73 (br d, J = 8 Hz, 2H), 8.17 (s, 1H); LCMS 227.4 [(M − H₂O) + 1] 17

  (6S)-6-amino-4-hydroxy-3-methyl-2-phenyl-2,4,6,7-tetrahydro-5H-pyrazolo[4,3-b]pyridin-5- one, trifluoroacetatesalt Ex 1⁴ 2.43 (s, 3H), 3.11 (dd, J = 14.9, 14.0 Hz, 1H), 3.31-3.37 (m,1H, assumed; partially obscured by solvent peak), 4.50 (dd, J = 13.9,7.1 Hz, 1H), 7.43-7.58 (m, 5H); 259.4 18

  (5S)-5-amino-7-hydroxy-1-methyl-1,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin- 6-one, trifluoroacetatesalt Ex 1⁵ 2.85 (ddd, J = 14.5, 13.9, 0.6 Hz, 1H), 3.16 (dd, J = 14.5,7.3 Hz, 1H), 3.95 (s, 3H), 4.43 (dd, J = 13.9, 7.3 Hz, 1H), 7.30 (d, J =0.5 Hz, 1H); LCMS m/z 181.2 (M − 1) 19

  (5S)-5-amino-2-cyclobutyl-7-hydroxy-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6- one, HCl salt Ex 1 ¹HNMR (400 MHz, DMSO-d₆) δ: 1.69-1.80 (m, 2H), 2.28-2.44 (m, 4H), 2.74 (brdd, J = 14, 14 Hz, 1H), 3.09 (br dd, J = 14, 7 Hz, 1H), 4.33-4.43 (br m,1H), 4.67-4.77 (m, 1H), 7.67 (s, 1H), 8.56 (br s, 3H), 10.74 (br s, 1H);223.2 20

  (5S)-5-amino-7-hydroxy-2-isopropyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin- 6-one, HCl salt Ex 1 ¹HNMR (300 MHz, DMSO-d₆) δ: 1.37 (d, J = 6.6 Hz, 6H), 2.74 (br dd, J = 14,14 Hz, 1H), 3.10 (dd, J = 14.6, 7.3 Hz, 1H), 4.31-4.44 (m, 2H), 7.64 (s,1H), 8.60 (br s, 3H), 10.70 (s, 1H); 211.0 21

  (5S)-5-amino-7-hydroxy-3-(4-methoxybenzyl)-1-methyl-1,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin- 6-one,trifluoroacetate salt Ex 3⁶ ¹H NMR (300 MHz, CD₃OD) δ: 2.54 (dd, J =14.3, 13.9 Hz, 1H), 2.85 (dd, J = 14.5, 7.5 Hz, 1H), 3.75 (s, 3H), 3.83(br s, 2H), 3.92 (s, 3H), 4.33 (dd, J = 13.8, 7.3 Hz, 1H), 6.84 (br d, J= 8.7 Hz, 2H), 7.12 (br d, J = 8.7 Hz, 2H); 303.2 22

  (5S)-5-amino-7-hydroxy-3-(3-methoxybenzyl)-1-methyl-1,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin- 6-one,trifluoroacetate salt Ex 3⁶ ¹H NMR (300 MHz, CD₃OD) δ: 2.56 (dd, J =14.1, 14.1 Hz, 1H), 2.89 (dd, J = 14.5, 7.5 Hz, 1H), 3.75 (s, 3H), 3.87(br s, 2H), 3.93 (s, 3H), 4.34 (dd, J = 13.8, 7.5 Hz, 1H), 6.74-6.83 (m,3H), 7.20 (dd, J = 9.0, 7.2 Hz, 1H); 303.3 23

  (5S)-5-amino-3-benzyl-2-ethyl-7-hydroxy-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin- 6-one, HCl salt Ex 3⁷ ¹HNMR (400 MHz, CD₃OD) δ: 1.20 (t, J = 7.2 Hz, 3H), 2.67 (dd, J = 14, 14Hz, 1H), 2.96 (br dd, J = 14.5, 7.4 Hz, 1H), 3.99-4.13 (m, 4H), 4.37(dd, J = 13.5, 7.4 Hz, 1H), 7.18-7.22 (m, 2H), 7.23-7.28 (m, 1H),7.31-7.36 (m, 2H); 287.0 24

  (5S)-5-amino-3-benzyl-7-hydroxy-2-isopropyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin- 6-one, HCl salt Ex 3⁷ ¹HNMR (300 MHz, CD₃OD) δ: 1.28 (d, J = 6.6 Hz, 3H), 1.29 (d, J = 6.5 Hz,3H), 2.73 (dd, J = 14, 14 Hz, 1H), 3.05 (dd, J = 14.5, 7.3 Hz, 1H), 4.08(AB quartet, J_(AB) = 17 Hz, Δν_(ab) = 8 Hz, 2H), 4.33-4.52 (m, 2H),7.15-7.37 (m, 5H); 301.0 25

  (5S)-5-amino-7-hydroxy-2-methyl-3-[3-(trifluoromethyl)benzyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one, HCl salt Ex 3⁷ ¹H NMR (300 MHz, CD₃OD) δ:2.67 (dd, J = 14.3, 13.8 Hz, 1H), 2.95 (dd, J = 14.5, 7.5 Hz, 1H), 3.69(s, 3H), 4.19 (AB quartet, J_(AB) = 16.7 Hz, Δν_(AB) = 11.3 Hz, 2H),4.37 (dd, J = 13.6, 7.5 Hz, 1H), 7.43-7.62 (m, 4H); 341.0 26

  (5S)-5-amino-7-hydroxy-2-methyl-3-[2-(trifluoromethyl)benzyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one, HCl salt Ex 3⁷ ¹H NMR (300 MHz, CD₃OD) δ:2.53 (dd, half of ABX pattern, J = 14.4, 13.7 Hz, 1H), 2.67 (dd, half ofABX pattern, J = 14.5, 7.7 Hz, 1H), 3.68 (s, 3H), 4.27 (br s, 2H), 4.31(dd, J = 13.4, 7.7 Hz, 1H), 7.19 (br d, J = 7.5 Hz, 1H), 7.49 (br dd, J= 8, 7 Hz, 1H), 7.56- 7.63 (m, 1H), 7.78 (br d, J = 7 Hz, 1H); 340.9 27

  (5S)-5-amino-7-hydroxy-2-methyl-3-[4-(trifluoromethyl)benzyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one, HCl salt Ex 3⁷ ¹H NMR (300 MHz, CD₃OD) δ:2.69 (dd, J = 14.1, 13.9 Hz, 1H), 2.99 (dd, J = 14.5, 7.4 Hz, 1H), 3.69(s, 3H), 4.18 (AB quartet, J_(AB) = 16.9 Hz, Δν_(AB) = 9.4 Hz, 2H), 4.39(dd, J = 13.6, 7.5 Hz, 1H), 7.40 (d, J = 8.0 Hz, 2H), 7.65 (d, J = 8.0Hz, 2H); 340.9 28

  (5S)-5-amino-7-hydroxy-2-[2-(trifluoromethyl)phenyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one, HCl salt Ex 7 2.96(ddd, J = 14.7, 13.7, 1.3 Hz, 1H), 3.36 (dd, J = 14.8, 7.4 Hz, 1H), 4.51(dd, J = 13.7, 7.4 Hz, 1H), 7.59 (br d, J = 8.0 Hz, 1H), 7.71 (br dd, J= 8, 8 Hz, 1H), 7.76 (br s, 1H), 7.78-7.83 (m, 1H), 7.88-7.92 (m, 1H);313.1 29

  (5S)-5-amino-7-hydroxy-2-[4-(trifluoromethyl)phenyl]-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one, HCl salt Ex 1⁸ 2.97(ddd, J = 14.7, 13.6, 1.4 Hz, 1H), 3.38 (br dd, J = 14.8, 7.3 Hz, 1H),4.50 (dd, J = 13.6, 7.3 Hz, 1H), 7.78 (br d, J = 9 Hz, 2H), 7.94 (br d,J = 9 Hz, 2H), 8.28 (br d, J = 1 Hz, 1H); 313.41. The more polar regioisomer produced during the synthesis of C30 inExample 4 was employed as starting material in place of C20.2. C1 was converted to the requisite N-phenyl pyrazole starting material(employed in place of C20) using the chemistry described for synthesisof C56 in Example 7. See also P. Y. S. Lam et al., Tetrahedron Lett.1998, 39, 2941-2944.3. Arylation of C29, followed by ester hydrolysis, to provide4-nitro-1-phenyl-1H-pyrazole-3-carboxylic acid may be carried outaccording to T. A. Miller et al., PCT Int. Appl. 2007, WO 2007087129 A2.Subsequent conversion of the carboxylic acid moiety to a primary bromidemay be effected as described in Example 2. The resulting3-(bromomethyl)-4-nitro-1-phenyl-1H-pyrazole was converted to3-(4-nitro-1-phenyl-1H-pyrazol-3-yl)alanine using chemistry reported byF. Crestey et al., Tetrahedron 2006, 62, 7772-7775; this compound wasused in place of C6.4. 5-Methyl-4-nitro-1H-pyrazole-3-carboxylic acid was converted to thecorresponding methyl ester, and then N-arylated using the chemistrydescribed in footnote 2. The more polar product upon silica gelchromatography (methyl5-methyl-4-nitro-1-phenyl-1H-pyrazole-3-carboxylate) was used in placeof C1.5. 1-Methyl-5-nitro-1H-pyrazole-4-carboxylic acid was reduced to theprimary alcohol using sodium borohydride and boron trifluoridedimethylate etherate; this alcohol was used in place of C3.6. Sodium hydride-mediated reaction of ethyl cyanoacetate with asubstituted phenylacetyl chloride afforded the appropriately substitutedethyl 2-cyano-3-hydroxy-4-(4-phenyl)but-2-enoate, which was alkylatedwith ethyl iodide in the presence of silver carbonate to yield thecorresponding ethyl 2-cyano-3-ethoxy-4-(4-phenyl)but-2-enoate. Reactionwith methylhydrazine in methanol at reflux provided the requisitesubstituted ethyl 5-amino-3-(benzyl)-1-methyl-1H-pyrazole-4-carboxylate;this was used as starting material. See Y. Xia et al., J. Med. Chem.1997, 40, 4372-4377.7. The appropriately substituted ethyl2-cyano-3-hydroxy-4-(4-phenyl)but-2-enoate, prepared as described infootnote 6, was converted to the corresponding ethyl3-chloro-2-cyano-4-phenylbut-2-enoate by reaction with phosphorusoxychloride and tributylamine. Reaction with the benzaldehyde hydrazoneof the requisite substituted hydrazine afforded a 1-substituted ethyl3-amino-5-benzyl-1H-pyrazole-4-carboxylate, which was used as startingmaterial. See Y. Xia et al., J. Med. Chem. 1997, 40, 4372-4377.8. C1 was subjected to a Suzuki reaction with[4-(trifluoromethyl)phenyl]boronic acid; the resulting ethyl3-nitro-1-[4-(trifluoromethyl)phenyl]-1H-pyrazole-4-carboxylate was usedin place of C2.

KAT II Inhibition Spectra Assay

Formation of kynurenic acid (KYNA) is indirectly assessed by a decreasein light absorbance at 370 nm (OD370) as the L-kynurenine (KYN)substrate is converted by the human KAT II (hKAT II) enzyme into KYNA.An inhibitor would therefore inhibit the decrease in OD370.

The protocol was performed by placing the following reagents into aCostar 384 well black plate (30 μL total assay volume/well):

-   -   10 μL of 3× concentrated compound;    -   10 μL of 3× concentrated substrate mix (BGG (Sigma G-5009); 3 mM        L-Kynurenine in 150 mM Tris Acetate (Sigma K3750); 3 mM        α-ketoglutaric acid in 150 mM Tris Acetate (Sigma K2010); and        210 μM pyridoxal 5-phosphate (PLP) in 150 mM Tris Acetate (Sigma        9255)); and    -   10 μL of 3× concentrated enzyme (15 nM enzyme in 150 mM Tris        Acetate with 0.3% bovine serum).

Plates were sealed and incubated at 37° C. for 15-20 h before readingOD370 on a SpectraMax Plus plate reader. IC₅₀s were generated bycomparing the efficacy of compounds across a concentration range toinhibit a reduction in the OD370 value relative to assay wells with DMSOadded in place of concentrated compound. Biological data for theExamples may be found in Table 2.

TABLE 2 KATII IC₅₀ (nM; single determination unless otherwise Ex No.indicated) 1  59.4 2  63.7¹ 3  11.5 4  22.5¹ 5  42.7 6  43.6¹ 7  74.7¹ 8 36.0 9  117 10  50.2 11   8.93 12  81.6 13  182 14  24.3¹ 15  28.3¹ 16 85.0¹ 17 2010¹ 18  329 19  81.3 20  153 21  440 22  65.6 23  24.3 24 63.0 25  42.2 26  40.7 27  37.0¹ 28  38.8 29  31.6 ¹Value representsthe average of 2 IC₅₀ determinations

What is claimed is:
 1. A compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein solid circlerepresents single or double bonds as valency requires; X, Y, and Z areindependently selected from a group consisting of ═N—, —N═, NR¹, andCR², provided that at least two are other than CR²; R¹ is H, alkyl,cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, SO₂NR⁵R⁶, orSO₂R^(5a), wherein each said alkyl, cycloalkyl, heterocycloalkyl, aryl,aralkyl, and heteroaryl may be substituted with one or more substituentsindependently selected from hydroxy, amino, halo, alkyl, haloalkyl, CN,alkoxy, haloalkoxy, alkylamino, aminoalkyl, —(CH₂)_(n)cycloalkyl,—(CH₂)_(n)heterocycloalkyl, —(CH₂)_(n)aryl, and —(CH₂)_(n)heteroaryl; R²is H, halo, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl,heteroaryl, alkoxy, cycloalkyloxy, aryloxy, aralkyloxy,heterocycloalkyloxy, heteroaryloxy, CN, —(CH₂)_(n)NR⁵R⁶, C(═O)NR⁵R⁶,SO₂NR⁵R⁶, SO₂R^(5a), NR⁵SO₂R^(5a), or NR⁵C(═O)R^(5a), wherein each saidalkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkoxy,cycloalkyloxy, aryloxy, aralkyloxy, heterocycloalkyloxy, andheteroaryloxy may be substituted with one or more substituentsindependently selected from hydroxy, amino, halo, alkyl, haloalkyl, CN,alkoxy, haloalkoxy, alkylamino, aminoalkyl, —(CH₂)_(n)cycloalkyl,—(CH₂)_(n)heterocycloalkyl, —(CH₂)_(n)aryl, and —(CH₂)_(n)heteroaryl; R³is H, C(═O)R⁷, C(═O)OR⁷, C(═O)NR^(7a)R^(7b), or (CH₂)R⁸; each R⁴ isindependently H, methyl, or fluoromethyl; R⁵ and R⁶ are independently H,alkyl, fluoroalkyl, aryl, or heteroaryl, or R⁵ and R⁶ of C(═O)NR⁵R⁶ orSO₂NR⁵R⁶, together with the nitrogen to which they are attached, mayform a heterocycloalkyl; R^(5a) is alkyl, fluoroalkyl, aryl, orheteroaryl; R⁷ is alkyl, aryl, heteroaryl, or cycloalkyl, wherein eachsaid alkyl, aryl, heteroaryl, and cycloalkyl may be substituted with oneor more substituents independently selected from hydroxy, amino, halo,alkoxy, and aminoalkyl; R^(7a) and R^(7b) are independently H, alkyl,aryl, heteroaryl, or cycloalkyl, wherein each said alkyl, aryl,heteroaryl, and cycloalkyl may be substituted with one or moresubstituents independently selected from hydroxy, amino, halo, alkoxy,and aminoalkyl, or, when R³ is C(═O)NR^(7a)R^(7b), R^(7a) and R^(7b),together with the nitrogen atom to which they are attached, may form a5- or 6-membered N-containing heterocyclic ring; R⁸ is

R⁹ is H, alkyl, aryl, heteroaryl, or cycloalkyl, wherein each saidalkyl, aryl, heteroaryl, and cycloalkyl may be substituted with one ormore substituents independently selected from hydroxy, amino, halo,alkoxy, and aminoalkyl; and each n is independently 0, 1, 2, or
 3. 2.The compound of claim 1, or a pharmaceutically acceptable salt thereof,wherein one of X or Y is NR¹ and the other is —N═ or ═N—; Z is CR²; R¹is C₁ to C₆ alkyl; C₃ to C₆ cycloalkyl, aryl, or arylalkyl; R² is H, C₁to C₆ alkyl, C₃ to C₆ cycloalkyl, aryl or arylalkyl; and wherein eachsaid alkyl, cycloalkyl, aryl, and arylalkyl may be substituted asallowed in claim 1 and R³ and R⁴ are as defined in claim
 1. 3. Thecompound of claim 1, or a pharmaceutically acceptable salt thereof,wherein X is NR¹; Y is —N═ or ═N—; and Z is CR².
 4. The compound ofclaim 1, or a pharmaceutically acceptable salt thereof, wherein thealkyl of R¹ is C₁ to C₃ alkyl.
 5. The compound of claim 1, or apharmaceutically acceptable salt thereof, wherein the aryl of R¹ and R²is phenyl or naphthyl, and the arylalkyl of R¹ and R² is —CH₂-phenyl or—CH₂-naphthyl, and wherein each said phenyl or naphthyl may besubstituted with one or more substituents independently selected fromhalo, alkyl, haloalkyl, alkoxy, haloalkoxy, and CN.
 6. The compound ofclaim 1, or a pharmaceutically acceptable salt thereof, wherein X is —N═or ═N—; Y is NR¹; Z is CR²; R¹ is C₁ to C₆ alkyl; R² is H, aryl orarylalkyl; and wherein each said alkyl, aryl, and arylalkyl may besubstituted as allowed in claim
 1. 7. The compound of claim 6, or apharmaceutically acceptable salt thereof, wherein the aryl of R² isphenyl or naphthyl, and the arylalkyl of R² is —CH₂-phenyl or—CH₂-naphthyl, and wherein each said phenyl or naphthyl may besubstituted with one or more substituents independently selected fromhalo, alkyl, haloalkyl, alkoxy, haloalkoxy, and CN.
 8. The compound ofclaim 1, or a pharmaceutically acceptable salt thereof, wherein X isCR²; Y is NR¹; and Z is —N═ or ═N—; R¹ is H, C₁ to C₆ alkyl, aryl orarylalkyl; R² is H or C₁ to C₃ alkyl; and wherein each said alkyl, aryland arylalkyl may be substituted as allowed in claim
 1. 9. The compoundof claim 1, or a pharmaceutically acceptable salt thereof, wherein X isCR²; Y is —N═ or ═N—; and Z is NR¹; R¹ is H, C₁ to C₆ alkyl, aryl orarylalkyl; R² is H or C₁ to C₃ alkyl; and wherein each said alkyl, aryland arylalkyl may be substituted as allowed in claim
 1. 10. The compoundof claim 8, or a pharmaceutically acceptable salt thereof, wherein thearyl of R¹ is phenyl or naphthyl, and the arylalkyl of R¹ is —CH₂-phenylor —CH₂-naphthyl, and wherein each said phenyl or naphthyl may besubstituted with one or more substituents independently selected fromhalo, alkyl, haloalkyl, alkoxy, haloalkoxy, and CN.
 11. The compound ofclaim 9, or a pharmaceutically acceptable salt thereof, wherein the arylof R¹ is phenyl or naphthyl, and the arylalkyl of R¹ is —CH₂-phenyl or—CH₂-naphthyl, and wherein each said phenyl or naphthyl may besubstituted with one or more substituents independently selected fromhalo, alkyl, haloalkyl, alkoxy, haloalkoxy, and CN.
 12. The compound ofclaim 1, or a pharmaceutically acceptable salt thereof, wherein R³ is Hand each R⁴ is H.
 13. The compound of claim 1, or a pharmaceuticallyacceptable salt thereof wherein the NH₂ of compounds of formula I hasthe following stereochemistry:


14. A compound of claim 1 selected from:(5S)-5-Amino-2-benzyl-7-hydroxy-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one;(5S)-5-Amino-3-benzyl-7-hydroxy-1-methyl-1,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one;(5S)-5-amino-7-hydroxy-2-phenyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one;and(5S)-5-amino-3-benzyl-2-ethyl-7-hydroxy-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one,or a pharmaceutically acceptable salt thereof.
 15. A compound that is(5S)-5-amino-7-hydroxy-2-phenyl-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-oneor a pharmaceutically acceptable salt thereof.
 16. A pharmaceuticalcomposition comprising a compound of claim 1, or a pharmaceuticallyacceptable salt thereof, and a pharmaceutically acceptable carrier. 17.A pharmaceutical composition comprising a compound of claim 14, or apharmaceutically acceptable salt thereof, and a pharmaceuticallyacceptable carrier.
 18. A pharmaceutical composition comprising acompound of claim 15, or a pharmaceutically acceptable salt thereof, anda pharmaceutically acceptable carrier.
 19. A method for treating orpreventing a condition in a mammal selected from the group consisting ofacute neurological and psychiatric disorders; stroke; cerebral ischemia;spinal cord trauma; cognitive impairment; head trauma; perinatalhypoxia; cardiac arrest; hypoglycemic neuronal damage; dementia;Alzheimer's disease; Huntington's Chorea; amyotrophic lateral sclerosis;ocular damage; retinopathy; cognitive disorders; idiopathic anddrug-induced Parkinson's disease; muscular spasms and disordersassociated with muscular spasticity; epilepsy; convulsions; migraine;urinary incontinence; substance tolerance; substance withdrawal;psychosis; schizophrenia; negative symptoms associated withschizophrenia; autism; bipolar disorder; depression; cognitiveimpairment associated with depression; cognitive impairment associatedwith cancer therapy; anxiety; mood disorders; inflammatory disorders;sepsis; cirrhosis; cancer and/or tumors associated with immune responseescape; trigeminal neuralgia; hearing loss; tinnitus; maculardegeneration of the eye; emesis; brain edema; pain; tardive dyskinesia;sleep disorders; attention deficit/hyperactivity disorder; attentiondeficit disorder; disorders that comprise as a symptom a deficiency inattention and/or cognition; and conduct disorder; which method comprisesadministering to the mammal a therapeutically effective amount of acompound of claim 1 or a pharmaceutically acceptable salt thereof. 20.The method according to claim 19 wherein the condition is dementia;cognitive deficit symptoms of Alzheimer's disease; attention deficitsymptoms of Alzheimer's disease; multi-infarct dementia, alcoholicdementia or other drug-related dementia, dementia associated withintracranial tumors or cerebral trauma, dementia associated withHuntington's disease or Parkinson's disease, or AIDS-related dementia;delirium; amnestic disorder; post-traumatic stress disorder; mentalretardation; a learning disorder; attention-deficit/hyperactivitydisorder; age-related cognitive decline; cognitive deficits associatedwith psychoses; or cognitive deficits associated with schizophrenia.